Exhaust aftertreatment component condition estimation and regeneration

ABSTRACT

Described herein is an apparatus for an exhaust aftertreatment system includes a first aftertreatment component poison module that is configured to generate a first component poison regeneration request based on an estimated accumulation of a first poison on the first aftertreatment component. The accumulation of the first poison on the first aftertreatment component is based on an estimated amount of the first poison being released from the first aftertreatment component. The apparatus also includes a second aftertreatment component poison module that is configured to generate a second component poison regeneration request based on an estimated accumulation of the first poison on the second aftertreatment component. The accumulation of the first poison on the second aftertreatment component is based on the estimated amount of the first poison being released from the first aftertreatment component.

FIELD

This disclosure relates generally to internal combustion engine systems,and more particularly to estimating the accumulation of species oncomponents of an exhaust aftertreatment system and regenerating thecomponents of the exhaust aftertreatment system to remove theaccumulation of species.

BACKGROUND

Emissions regulations for internal combustion engines have become morestringent over recent years. Environmental concerns have motivated theimplementation of stricter emission requirements for internal combustionengines throughout much of the world. Governmental agencies, such as theEnvironmental Protection Agency (EPA) in the United States, carefullymonitor the emission quality of engines and set acceptable emissionstandards, to which all engines must comply. Consequently, the use ofexhaust aftertreatment systems on engines to reduce emissions isincreasing.

Generally, emission requirements vary according to engine type. Emissiontests for compression-ignition (diesel) engines typically monitor therelease of carbon monoxide (CO), unburned hydrocarbons (UHC), dieselparticulate matter (PM) such as ash and soot, and nitrogen oxides (NOx).Oxidation catalysts, such as diesel oxidation catalysts (DOC) have beenimplemented in exhaust gas aftertreatment systems to oxidize at leastsome particulate matter in the exhaust stream, reduce unburnedhydrocarbons and CO in the exhaust to less environmentally harmfulcompounds, and oxidize nitric oxide (NO) to form nitrogen dioxide (NO₂),which is used in the NOx conversion on an selective catalytic reduction(SCR) catalyst. To remove the particulate matter, a particulate matter(PM) filter is typically installed downstream from the oxidationcatalyst or in conjunction with the oxidation catalyst. However, someexhaust aftertreatment systems do not have a PM filter. With regard toreducing NOx emissions, NOx reduction catalysts, including SCR systems,are utilized to convert NOx (NO and NO₂ in some fraction) to N₂ andother compounds. Further, some systems include an ammonia oxidation(AMOX) catalyst downstream of the SCR catalyst to convert at least someammonia slipping from the SCR catalyst to N₂ and other less harmfulcompounds.

Exhaust aftertreatment system components can be susceptible to theaccumulation of various materials on the components. In most cases, suchmaterial accumulations or deposits negatively affect the operation,performance, or efficiency of the components. Accordingly, the materialsthat accumulate on aftertreatment components and negatively affect thefunctionality of the components can be considered poisons. Severalpoisonous materials include sulfur, unburned hydrocarbons (HC), andwater. For example, accumulations or deposits of sulfur-containingspecies on the DOC tends to decrease the conversion of NO to NO₂,decrease the conversion of HC to CO₂ and heat, which affects the thermalmanagement of an engine system, and increase the presence oraccumulation of HC in the DOC, which correspondingly decreases theconversion of NO to NO₂. Additionally, the presence of sulfur depositson the SCR catalyst decreases the NOx-conversion capability of the SCRcatalyst, and the presence of sulfur deposits on the AMOX catalystdecreases the ammonia-conversion capability of the AMOX catalyst.

The accumulation of HC species and water on the DOC, SCR catalyst, andAMOX catalyst can cause similar negative effects on the functionality ofthese components. Additionally, accumulation of HC species on the DOC inthe presence of an increase in the temperature of the DOC may causeuncontrolled light-off events or runaway regeneration. Such light-offevents may damage the DOC and send damaging sintered elements of the DOCinto the SCR catalyst and AMOX catalyst.

Because of the negative side-effects of sulfur, HC, and water speciesaccumulation on aftertreatment components, conventional exhaustaftertreatment systems conduct a periodic regeneration of the componentsto remove the accumulated species. Most periodic regeneration events areinitiated based on the passing of a preset period of time or apredetermined amount of fuel consumed by the engine regardless of theamount of accumulated poisonous species on the various components of theexhaust aftertreatment system.

SUMMARY

The subject matter of the present application has been developed inresponse to the present state of the art, and in particular, in responseto the problems and needs in the art that have not yet been fully solvedby currently available exhaust aftertreatment systems. Accordingly, thesubject matter of the present application has been developed to providemethods, systems, and apparatus for estimating conditions of componentsof an exhaust aftertreatment system, and regenerating the system basedon the estimated conditions. Generally, according to one embodiment,disclosed herein is an improved method, system, and apparatus forindividually and separately estimating the accumulation of a poisonousspecies (e.g., sulfur, HC, and/or water) on multiple components of anexhaust aftertreatment system, and regenerating the multiple componentsof the system based on an estimated species accumulation of a singlecomponent reaching a predetermined threshold.

According to one embodiment, an apparatus for an exhaust aftertreatmentsystem includes a first aftertreatment component poison module that isconfigured to generate a first component poison regeneration requestbased on an estimated accumulation of a first poison on the firstaftertreatment component. The accumulation of the first poison on thefirst aftertreatment component is based on an estimated amount of thefirst poison being released from the first aftertreatment component. Theapparatus also includes a second aftertreatment component poison modulethat is configured to generate a second component poison regenerationrequest based on an estimated accumulation of the first poison on thesecond aftertreatment component. The accumulation of the first poison onthe second aftertreatment component is based on the estimated amount ofthe first poison being released from the first aftertreatment component.

According to some implementations, the apparatus also includes a poisonregeneration arbitration module that is configured to generate a poisonregeneration command based on an arbitration of the first and secondcomponent poison regeneration requests. The apparatus can also include atime-based regeneration module that is configured to generate a systemregeneration request based on the passage of a preset period of time.The first poison regeneration arbitration module can be configured togenerate the poison regeneration command based on an arbitration of thefirst component poison regeneration request, second component poisonregeneration request, and system regeneration request.

In some implementations of the apparatus, the accumulation of the firstpoison on the second aftertreatment component is based on an estimatedamount of the first poison being released from the second aftertreatmentcomponent. The apparatus can further include a third aftertreatmentcomponent poison module that is configured to generate a third componentpoison regeneration request based on an estimated accumulation of thefirst poison on the third aftertreatment component. The accumulation ofthe first poison on the third aftertreatment component being can bebased on the estimated amount of the first poison being released fromthe second aftertreatment component.

According to certain implementations of the apparatus, the firstaftertreatment component poison module is configured to estimate anamount of the first poison being stored on the first aftertreatmentcomponent. The accumulation of the first poison on the firstaftertreatment component can be based on a difference between the amountof the first poison being stored on the first aftertreatment componentand the amount of the first poison being released from the firstaftertreatment component. The second aftertreatment component poisonmodule can be configured to estimate an amount of the first poison beingstored on the second aftertreatment component. The accumulation of thefirst poison on the second aftertreatment component can be based on adifference between the amount of the first poison being stored on thesecond aftertreatment component and the amount of the first poison beingreleased from the second aftertreatment component. The amount of thefirst poison being stored on the first aftertreatment component can beestimated based on a temperature of the first aftertreatment componentand a mass flow rate of exhaust gas into the first aftertreatmentcomponent. The amount of the first poison being stored on the secondaftertreatment component can be estimated based on a temperature of thesecond aftertreatment component and a mass flow rate of exhaust gas intothe second aftertreatment component. The amount of the first poisonbeing released from the first aftertreatment component can be estimatedbased on the temperature of the first aftertreatment component and theamount of the first poison being stored on the first aftertreatmentcomponent. The amount of the first poison being released from the secondaftertreatment component can be estimated based on the temperature ofthe second aftertreatment component and the amount of the first poisonbeing stored on the second aftertreatment component.

In some implementations of the apparatus, the first component poisonregeneration request includes first regeneration event parameters, andthe second component poison regeneration request includes secondregeneration event parameters. The first regeneration event parameterscan be different than the second regeneration event parameters. Thefirst poison can be one of sulfur, hydrocarbon, or water. The firstaftertreatment component can include one of a diesel oxidation catalyst,a diesel particulate filter, a selective catalytic reduction catalyst,or an ammonia oxidation catalyst, and the second aftertreatmentcomponent can include another one of the diesel oxidation catalyst,diesel particulate filter, selective catalytic reduction catalyst, orammonia oxidation catalyst.

According to some implementations, the apparatus additionally includes athird aftertreatment component poison module that is configured togenerate a third component poison regeneration request based on anestimated accumulation of a second poison on the first aftertreatmentcomponent. The accumulation of the second poison on the firstaftertreatment component can be based on an amount of the second poisonbeing released from the first aftertreatment component. The apparatusmay also include

a fourth aftertreatment component poison module that is configured togenerate a fourth component poison regeneration request based on anestimated accumulation of the second poison on the second aftertreatmentcomponent. The accumulation of the second poison on the secondaftertreatment component being can be based on the estimated amount ofthe second poison being released from the first aftertreatmentcomponent. The poison regeneration arbitration module may be configuredto generate the poison regeneration command based on an arbitration ofthe first, second, third, and fourth component poison regenerationrequests.

In some implementations, the first aftertreatment component poisonmodule generates the first component poison regeneration request whenthe estimated accumulation of the first poison on the firstaftertreatment component meets a first poison accumulation threshold.The first poison accumulation threshold can correspond with a minimumallowable performance characteristic of the first aftertreatmentcomponent. The second aftertreatment component poison module cangenerate the second component poison regeneration request when theestimated accumulation of the first poison on the second aftertreatmentcomponent meets a second poison accumulation threshold. The secondpoison accumulation threshold can correspond with a minimum allowableperformance characteristic of the second aftertreatment component. Thefirst poison accumulation threshold can be different than the secondpoison accumulation threshold. According to certain implementations, thefirst aftertreatment component includes one of a diesel oxidationcatalyst, a selective catalytic reduction catalyst, or an ammoniaoxidation catalyst, and the minimum allowable performance characteristicof the first aftertreatment component includes one of a minimumallowable NO to NO₂ oxidation efficiency, a minimum allowable NOxconversion efficiency, or a minimum allowable ammonia oxidationefficiency, respectively. According to yet certain implementations, thesecond aftertreatment component includes another one of the dieseloxidation catalyst, selective catalytic reduction catalyst, or ammoniaoxidation catalyst, and the minimum allowable performance characteristicof the second aftertreatment component includes one of the minimumallowable NO to NO₂ oxidation efficiency, minimum allowable NOxconversion efficiency, or minimum allowable ammonia oxidationefficiency, respectively.

In some implementations of the apparatus, the first poison includeshydrocarbon. At least the first aftertreatment component poison modulecan include an exothermal module configured to monitor an exothermalcondition of the first aftertreatment component. The firstaftertreatment component poison module generates an exothermalregeneration request when the exothermal condition meets an exothermalcondition threshold.

According to another embodiment, an exhaust aftertreatment system inexhaust gas receiving communication with an internal combustion engineincludes a DOC, an SCR catalyst downstream of the DOC, and an AMOXcatalyst downstream of the SCR catalyst. The system also includes a DOCpoison module that is configured to estimate an accumulation of a firstpoison on the DOC, and configured to request regeneration of the DOCwhen the accumulation of the first poison on the DOC meets a firstpredetermined poison accumulation threshold corresponding with a minimumdesirable NO to NO₂ oxidation efficiency of the DOC. Additionally, thesystem includes an SCR poison module that is configured to estimate anaccumulation of the first poison on the SCR catalyst, and configured torequest regeneration of the SCR catalyst when the accumulation of thefirst poison on the SCR catalyst meets a second predetermined poisonaccumulation threshold corresponding with a minimum desirable NOxconversion efficiency of the SCR catalyst. Also, the system includes anAMOX poison module that is configured to estimate an accumulation of thefirst poison on the AMOX catalyst, and configured to requestregeneration of the AMOX catalyst when the accumulation of the firstpoison on the AMOX catalyst meets a third predetermined poisonaccumulation threshold corresponding with a minimum desirable ammoniaoxidation efficiency of the AMOX catalyst.

In some implementations of the system, the DOC poison module is furtherconfigured to estimate an amount of poison being released from theinternal combustion engine and an amount of poison being released fromthe DOC. The estimate of the accumulation of the first poison on the DOCcan be based on the amount of poison being released from the internalcombustion engine. The SCR poison module can be further configured toestimate an amount of poison being released from the SCR catalyst. Theestimate of the accumulation of the first poison on the SCR catalyst canbe based on the amount of poison being released from the DOC. Theestimate of the accumulation of the first poison on the AMOX catalystcan be based on the amount of poison being released from the SCRcatalyst.

In yet another embodiment, a method for estimating conditions of andregenerating exhaust aftertreatment system components include estimatingan accumulated quantity of a poison on a first aftertreatment component.The method also includes commanding a regeneration of the exhaustaftertreatment system if the accumulated quantity of the poison on thefirst aftertreatment component meets a first threshold associated with aperformance characteristic of the first aftertreatment component.Further, the method includes estimating an accumulated quantity of thepoison on a second aftertreatment component, and commanding aregeneration of the exhaust aftertreatment system if the accumulatedquantity of the poison on the second aftertreatment component meets asecond threshold associated with a performance characteristic of thesecond aftertreatment component.

In some implementations, the method includes determining an amount ofthe poison entering the first aftertreatment component. Estimating theaccumulated quantity of the poison on the first aftertreatment componentcan be based on the amount of the poison entering the firstaftertreatment component. The method may also include estimating anamount of poison being released from the first aftertreatment component.Estimating the accumulated quantity of the poison on the secondaftertreatment component can be based on the amount of poison beingreleased from the first aftertreatment component.

In certain embodiments, the modules of the apparatus described hereinmay each include at least one of logic hardware and executable code, theexecutable code being stored on one or more memory devices. Theexecutable code may be replaced with a computer processor andcomputer-readable storage medium that stores executable code executed bythe processor.

Reference throughout this specification to features, advantages, orsimilar language does not imply that all of the features and advantagesthat may be realized with the subject matter of the present disclosureshould be or are in any single embodiment. Rather, language referring tothe features and advantages is understood to mean that a specificfeature, advantage, or characteristic described in connection with anembodiment is included in at least one embodiment of the presentdisclosure. Thus, discussion of the features and advantages, and similarlanguage, throughout this specification may, but do not necessarily,refer to the same embodiment.

The described features, structures, advantages, and/or characteristicsof the subject matter of the present disclosure may be combined in anysuitable manner in one or more embodiments and/or implementations. Inthe following description, numerous specific details are provided toimpart a thorough understanding of embodiments of the subject matter ofthe present disclosure. One skilled in the relevant art will recognizethat the subject matter of the present disclosure may be practicedwithout one or more of the specific features, details, components,materials, and/or methods of a particular embodiment or implementation.In other instances, additional features and advantages may be recognizedin certain embodiments and/or implementations that may not be present inall embodiments or implementations. Further, in some instances,well-known structures, materials, or operations are not shown ordescribed in detail to avoid obscuring aspects of the subject matter ofthe present disclosure. The features and advantages of the subjectmatter of the present disclosure will become more fully apparent fromthe following description and appended claims, or may be learned by thepractice of the subject matter as set forth hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the advantages of the subject matter may be more readilyunderstood, a more particular description of the subject matter brieflydescribed above will be rendered by reference to specific embodimentsthat are illustrated in the appended drawings. Understanding that thesedrawings depict only typical embodiments of the subject matter and arenot therefore to be considered to be limiting of its scope, the subjectmatter will be described and explained with additional specificity anddetail through the use of the drawings, in which:

FIG. 1 is a schematic diagram of an engine system having an internalcombustion engine and an exhaust aftertreatment system in accordancewith one representative embodiment;

FIG. 2 is a schematic block diagram of a controller of the engine systemof FIG. 1 in accordance with one representative embodiment;

FIG. 3 is a schematic block diagram of a sulfur oxidation module of thecontroller of FIG. 2 in accordance with one representative embodiment;

FIG. 4 is a schematic block diagram of a hydrocarbon oxidation module ofthe controller of FIG. 2 in accordance with one representativeembodiment; and

FIG. 5 is a schematic flow chart diagram of a method for diagnosing acondition of an exhaust aftertreatment component and correspondinglyregenerating the component in accordance with one representativeembodiment.

DETAILED DESCRIPTION

FIG. 1 depicts one embodiment of an engine system 10. The maincomponents of the engine system 10 include an internal combustion engine20 and an exhaust aftertreatment system 22 in exhaust gas-receivingcommunication with the engine 20. The internal combustion engine 20 canbe a compression-ignited internal combustion engine, such as adiesel-fueled engine, or a spark-ignited internal combustion engine,such as a gasoline-fueled engine operated lean. Although not shown, onthe air intake side, the engine system 10 can include an air inlet,inlet piping, a turbocharger compressor, and an intake manifold. Theintake manifold includes an outlet that is operatively coupled tocompression chambers of the internal combustion engine 20 forintroducing air into the compression chambers.

Within the internal combustion engine 20, air from the atmosphere iscombined with fuel, and combusted, to power the engine. The fuel comesfrom a fuel tank (not shown) through a fuel delivery system including,in one embodiment, a fuel pump and common rail to the fuel injectors,which inject fuel into the combustion chambers of the engine 20. Fuelinjection timing can be controlled by the controller 100 via a fuelinjector control signal.

Combustion of the fuel and air in the compression chambers of the engine20 produces exhaust gas that is operatively vented to an exhaustmanifold (not shown). From the exhaust manifold, a portion of theexhaust gas may be used to power a turbocharger turbine. Theturbocharger turbine drives the turbocharger compressor, which maycompress at least some of the air entering the air inlet beforedirecting it to the intake manifold and into the compression chambers ofthe engine 20.

The exhaust aftertreatment system 22 includes the controller 100 (whichalso can form part of the overall engine system 10), an optional dieselparticular filter (DPF) 40, a diesel oxidation catalyst (DOC) 30, aselective catalytic reduction (SCR) system 52 with an SCR catalyst 50,and an ammonia oxidation (AMOX) catalyst 60. The SCR system 52 furtherincludes a reductant delivery system that has a diesel exhaust fluid(DEF) source 54 that supplies DEF to a DEF doser 56 via a DEF orreductant delivery line 58.

In an exhaust flow direction, as indicated by directional arrow 29,exhaust gas flows from the engine 20 into inlet piping 24 of the exhaustaftertreatment system 22. From the inlet piping 24, the exhaust gasflows into the DOC 30 and exits the DOC into a first section of exhaustpiping 28A. From the first section of exhaust piping 28A, the exhaustgas flows into the DPF 40 if present and exits the DPF into a secondsection of exhaust piping 28B. From the second section of exhaust piping28B, the exhaust gas flows into the SCR catalyst 50 and exits the SCRcatalyst into the third section of exhaust piping 28C. As the exhaustgas flows through the second section of exhaust piping 28B, it isperiodically dosed with DEF by the DEF doser 56. Accordingly, the secondsection of exhaust piping 28B acts as a decomposition chamber or tube tofacilitate the decomposition of the DEF to ammonia. From the thirdsection of exhaust piping 28C, the exhaust gas flows into the AMOXcatalyst 60 and exits the AMOX catalyst into outlet piping 26 before theexhaust gas is expelled from the system 22. Based on the foregoing, inthe illustrated embodiment, the DOC 30 is position upstream of the DPF40 if present and the SCR catalyst 50, and the SCR catalyst 50 ispositioned downstream of the DPF 40 when present and upstream of theAMOX catalyst 60. However, in alternative embodiments, otherarrangements of the components of the exhaust aftertreatment system 22are also possible.

The DOC 30 can have any of various flow-through designs known in theart. Generally, the DOC 30 is configured to oxidize at least someparticulate matter, e.g., the soluble organic fraction of soot, in theexhaust and reduce unburned hydrocarbons and CO in the exhaust to lessenvironmentally harmful compounds. For example, the DOC 30 maysufficiently reduce the hydrocarbon and CO concentrations in the exhaustto meet the requisite emissions standards for those components of theexhaust gas. An indirect consequence of the oxidation capabilities ofthe DOC 30 is the ability of the DOC to oxidize NO into NO₂. In thismanner, the level of NO₂ exiting the DOC 30 is equal to the NO₂ in theexhaust gas generated by the engine 20 plus the NO₂ converted from NO bythe DOC. Accordingly, one metric for indicating the condition of the DOC30 is the NO₂/NOx ratio of the exhaust gas exiting the DOC.

In addition to treating the hydrocarbon and CO concentrations in theexhaust gas, the DOC 30 can also be used in the controlled regenerationof the DPF 40 when present, the SCR catalyst 50, and the AMOX catalyst60. This can be accomplished through the injection, or dosing, ofunburned HC into the exhaust gas upstream of the DOC 30. Upon contactwith the DOC 30, the unburned HC undergoes an exothermic oxidationreaction which leads to an increase in the temperature of the exhaustgas exiting the DOC 30 and subsequently entering the DPF 40, SCRcatalyst 50, and/or the AMOX catalyst 60. The amount of unburned HCadded to the exhaust gas is selected to achieve the desired temperatureincrease or target controlled regeneration temperature.

When present, the DPF 40 can be any of various flow-through designsknown in the art, and configured to reduce particulate matterconcentrations, e.g., soot and ash, in the exhaust gas to meet requisiteemission standards. According to certain applications, such as inemerging markets and developing countries, the exhaust aftertreatmentsystem 22 does not include a DPF 40. Because such systems lack a DPF 40,particulate matter and other constituents normally captured by a DPF arepassed and accumulate onto the SCR catalyst 50 and AMOX catalyst 60.Therefore, the need for a more precisely controlled and robust systemfor estimating the condition of components normally downstream of a DPF(e.g., the SCR catalyst 50 and AMOX catalyst 60) and regenerating thosecomponents when needed may be greater for systems without a DPF 40, thanthose systems with a DPF. Additionally, the DPF 40 when present may beconfigured to oxidize NO to form NO₂ independent of the DOC 30.

As discussed above, the SCR system 52 includes a reductant deliverysystem with a reductant (e.g., DEF) source 54, pump (not shown) anddelivery mechanism or doser 56. The reductant source 54 can be acontainer or tank capable of retaining a reductant, such as, forexample, ammonia (NH₃), DEF (e.g., urea), or diesel oil. The reductantsource 54 is in reductant supplying communication with the pump, whichis configured to pump reductant from the reductant source to thedelivery mechanism 56 via a reductant delivery line 58. The deliverymechanism 56 is positioned upstream of the SCR catalyst 50. The deliverymechanism 56 is selectively controllable to inject reductant directlyinto the exhaust gas stream prior to entering the SCR catalyst 50.

In some embodiments, the reductant can either be ammonia or DEF, whichdecomposes to produce ammonia. The ammonia reacts with NOx in thepresence of the SCR catalyst 50 to reduce the NOx to less harmfulemissions, such as N₂ and H₂O. The NOx in the exhaust gas streamincludes NO₂ and NO. Generally, both NO₂ and NO are reduced to N₂ andH₂O through various chemical reactions driven by the catalytic elementsof the SCR catalyst in the presence of NH₃. However, as discussed above,the chemical reduction of NO₂ to N₂ and H₂O typically is the mostefficient chemical reaction. Therefore, in general, the more NO₂ in theexhaust gas stream compared to NO, the more efficient the NO_(x)reduction performed by the SCR catalyst. Accordingly, the ability of theDOC 30 to convert NO to NO₂ directly affects the NOx reductionefficiency of the SCR system 52. Put another way, the NOx reductionefficiency of the SCR system 52 corresponds at least indirectly to thecondition or performance of the DOC 30. However, primarily, the NOxreduction efficiency of the SCR system 52 corresponds with the conditionor performance of SCR catalyst 50.

The SCR catalyst 50 can be any of various catalysts known in the art.For example, in some implementations, the SCR catalyst 50 is avanadium-based catalyst, and in other implementations, the SCR catalystis a zeolite-based catalyst, such as a Cu-Zeolite or a Fe-Zeolitecatalyst. In one representative embodiment, the reductant is aqueousurea and the SCR catalyst 50 is a zeolite-based catalyst.

The AMOX catalyst 60 can be any of various flow-through catalystsconfigured to react with ammonia to produce mainly nitrogen. Generally,the AMOX catalyst 60 is utilized to remove ammonia that has slippedthrough or exited the SCR catalyst 50 without reacting with NO_(x) inthe exhaust. In certain instances, the aftertreatment system 22 can beoperable with or without an AMOX catalyst. Further, although the AMOXcatalyst 60 is shown as a separate unit from the SCR catalyst 50, insome implementations, the AMOX catalyst can be integrated with the SCRcatalyst, e.g., the AMOX catalyst and the SCR catalyst can be locatedwithin the same housing. The condition of the AMOX catalyst 60 can berepresented by the performance of the AMOX catalyst (i.e., the abilityof the AMOX catalyst to convert ammonia into mainly nitrogen).

Various sensors, such as temperature sensors 12 and mass flow sensor 14,may be strategically disposed throughout the exhaust aftertreatmentsystem 22 and may be in communication with the controller 100 to monitoroperating conditions of the engine system 10. In one embodiment, thetemperature sensors 12 sense the temperature of exhaust gas flowingthrough the exhaust aftertreatment system 22 at various locations, andthe mass flow sensor 14 senses the rate at which the exhaust gas isflowing into and through the exhaust aftertreatment system. Althoughonly temperature and mass flow sensors 12, 14 are shown, in otherembodiments, the engine system 10 and exhaust aftertreatment system 22may include more or fewer sensors than those shown.

Although the exhaust aftertreatment system 22 shown includes one of anDOC 30, an optional DPF 40, SCR catalyst 50, and AMOX catalyst 60positioned in specific locations relative to each other along theexhaust flow path, in other embodiments, the exhaust aftertreatmentsystem may include more than one of any of the various catalystspositioned in any of various positions relative to each other along theexhaust flow path as desired. Further, although the DOC 30 and AMOXcatalyst 60 are non-selective catalysts, in some embodiments, the DOCand AMOX catalyst can be selective catalysts.

The controller 100 controls the operation of the engine system 10 andassociated sub-systems, such as the internal combustion engine 20 andthe exhaust gas aftertreatment system 22. The controller 100 is depictedin FIGS. 1 and 2 as a single physical unit, but can include two or morephysically separated units or components in some embodiments if desired.Generally, the controller 100 receives multiple inputs, processes theinputs, and transmits multiple outputs. The multiple inputs may includesensed measurements, from the sensors, estimates from virtual sensors,and various user inputs. For example, referring to FIG. 2, operatingconditions of the internal combustion engine 20 (e.g., engine conditioninputs 102), conditions of the exhaust gas (e.g., exhaust conditioninputs 104) flowing through the exhaust aftertreatment system 22, andtime condition inputs 106 can be ascertained from any of the physicalsensors, from any of various virtual sensors or models, user input,and/or via the controller's 100 commands to the engine, such as fuelrate, engine speed, engine load, and the like. The inputs are processedby the controller 100 using various algorithms, stored data, and otherinputs to update the stored data and/or generate output values. Thegenerated output values and/or commands are transmitted to othercomponents of the controller and/or to one or more elements of theengine system 10 to control the system to achieve desired results, andmore specifically, achieve desired exhaust gas emissions, and componentperformance and longevity.

Generally, the controller 100 includes various modules for controllingthe operation of the engine system 10. For example, the controller 100includes one or more modules for estimating conditions of the exhaustaftertreatment components 30, 40, 50, 60 and controlling theregeneration of the components. As is known in the art, the controller100 and its various modular components may comprise processor, memory,and interface modules that may be fabricated of semiconductor gates onone or more semiconductor substrates. Each semiconductor substrate maybe packaged in one or more semiconductor devices mounted on circuitcards. Connections between the modules may be through semiconductormetal layers, substrate-to-substrate wiring, or circuit card traces orwires connecting the semiconductor devices.

Referring to FIG. 2, the controller 100 includes a sulfur oxidationmodule 110 and a hydrocarbon oxidation module 120. Generally, the sulfurand hydrocarbon oxidation modules 110, 120 of the controller 100 receiveinputs 102, 104, 106 and generate a sulfur regeneration command 112 andhydrocarbon regeneration command 122, respectively, based on at leastone of the inputs. When generated, the commands 112, 122 communicateregeneration event parameters to the engine system 10. In response tothe commands 112, 122, various components or levers of the engine system10 are actuated to effectuate a regeneration event corresponding to theregeneration vent parameters of the commands. For example, theregeneration event parameters may include an exhaust temperatureparameter, an exhaust mass flow rate parameter, and a timing parameter,the engine system 10 actuates internal or external fuel dosingcomponents to increase the exhaust temperature and engine speed for aspecified time in accordance with the parameters. Once commanded, theregeneration events can be effectuated using any of various techniquesknown in the art as desired.

As shown in FIG. 3, the sulfur oxidation module 110 includes a DOCsulfur module 130, an SCR sulfur module 150, an AMOX sulfur module 170,and a sulfur regeneration arbitration module 190. Each of the DOCsulfur, SCR sulfur, and AMOX sulfur modules 130, 150, 170 generate arespective sulfur regeneration request 140, 160, 180 if certainestimated conditions are met. The sulfur regeneration requests 140, 160,180 are received by the sulfur regeneration arbitration module 190,which arbitrates between one or more sulfur regeneration requests, and atimer-based regeneration request, to generate the sulfur regenerationcommand 112. The sulfur regeneration command 112 then represents thecharacteristics of the winning regeneration request from the arbitrationprocess.

The DOC sulfur module 130 of the sulfur oxidation module 110 includes aDOC sulfur storage module 132, DOC sulfur release module 134, DOC sulfuraccumulation module 136, and DOC sulfur regeneration module 138. The DOCsulfur storage module 132 is configured to estimate the amount of sulfurbeing stored (e.g., adsorbed) on the DOC 30. As defined herein, sulfurcan include any of various sulfur compounds, such as, for example, SOx(e.g., SO₂ and SO₃), H₂SO₄, SOx on soot, and sulfates of ammonia andcopper. According to the illustrated embodiment, the DOC sulfur storagemodule 132 estimates the amount or quantity of sulfur being stored onthe DOC based on various inputs, such as, for example, the engine outsulfur (i.e., the quantity of sulfur in the exhaust gas exiting theengine 20 and entering the DOC 30), the temperature of the DOC, and themass flow rate of exhaust gas into the DOC. In certain implementations,the engine out sulfur is a function of the fuel rate 124 (i.e., the rateof fuel entering and being consumed by the engine 20), and the fuelsulfur 126 (i.e., the concentration of sulfur in the fuel beingconsumed). Generally, the engine out sulfur can be expressed in terms ofa volumetric or part-per-minute flow rate and is equal to a percentageof the fuel rate 124 multiplied by the fuel sulfur 126. The temperatureof the DOC 30 (e.g., the catalyst bed of the DOC) can be determined bythe DOC sulfur storage module 132 according to any of varioustechniques, such as using estimation modules and/or physical sensors.For example, the temperature of the DOC 30 can be determined based onthe difference between exhaust gas temperature measurements taken by thetemperature sensors 12 upstream and downstream of the DOC. Additionally,or alternatively, the exhaust aftertreatment system 22 may have a DOCmid-bed temperature sensor that more directly detects the temperature ofthe DOC 30.

According to one embodiment, the quantity of sulfur being stored on theDOC 30, which can be expressed as the rate of sulfur being stored on theDOC, for a given engine out sulfur value, can be obtained from a look-uptable that is stored on the DOC sulfur storage module 132 and includespredetermined sulfur storage rates on the DOC 30 compared to DOCtemperature values and exhaust mass flow rate values. The DOC sulfurstorage module 132 can include a plurality of look-up tables eachassociated with a given engine out sulfur value. Accordingly, once thetemperature of the DOC 30 and exhaust mass flow rate is determined orknown, the sulfur storage rate on the DOC estimated by the DOC sulfurstorage module 132 is the predetermined value in the look-up table(associated with the determined engine out sulfur value) for thedetermined DOC temperature and exhaust flow rate values. Generally, thesulfur adsorption rate on components is lower at higher exhaust gastemperatures. For engine out sulfur values between or outside thosecorresponding with the look-up tables, interpolation or extrapolationtechniques can be utilized to estimate the DOC sulfur storage rate.

The quantity of sulfur stored on the DOC 30 over a desired time period,which can be represented by the time input 192, is then estimated by theDOC sulfur storage module 132 by multiplying the estimated DOC sulfurstorage rate by the desired time period. In certain implementations, thequantity of sulfur stored on the DOC over the desired time periodrepresents an estimate of the newly stored sulfur, which can be added toa previous estimate of the accumulation of sulfur on the DOC 30, as willbe explained in more detail below, to obtain a more accurate estimate ofthe quantity of sulfur currently stored on the DOC.

The DOC sulfur release module 134 of the DOC sulfur module 130 isconfigured to estimate the DOC outlet sulfur 142 (i.e., the amount orquantity of sulfur being released (e.g., desorbed) from the DOC 30)based on various inputs, such as, for example, the temperature of theDOC and the quantity of sulfur stored on the DOC. Generally, the sulfurrelease rate from components is lower at higher exhaust gastemperatures. The DOC sulfur release module 134 may estimate thetemperature of the DOC 30 in the same or similar manner as the DOCsulfur storage module 132, or simply utilize the temperature of the DOCestimated by the DOC sulfur storage module. Similarly, the quantity ofsulfur stored on the DOC 30 can be obtained from the DOC sulfur storagemodule 132 or can be based on a previous estimate of the accumulation ofsulfur on the DOC.

According to one embodiment, the DOC outlet sulfur 142 or amount ofsulfur being released from the DOC 30, which can be expressed as therate of sulfur being released from the DOC, can be obtained from alook-up table that is stored on the DOC sulfur release module 134 andincludes predetermined sulfur release rates from the DOC 30 compared toDOC temperature values and DOC sulfur storage values. The DOC sulfurrelease module 134 can include a plurality of look-up tables eachassociated with a given DOC outlet sulfur value. Accordingly, once thetemperature of the DOC 30 and DOC outlet sulfur value is determined orknown, the sulfur release rate from the DOC estimated by the DOC sulfurrelease module 134 is the predetermined value in the look-up table forthe determined DOC temperature and DOC sulfur storage values. Thequantity of sulfur released from the DOC 30 over a desired time period(e.g., the same desired time period used by the DOC sulfur storagemodule 132 to estimate the DOC sulfur storage), which also can berepresented by the time input 192, is then estimated by the DOC sulfurrelease module 134 by multiplying the estimated DOC sulfur release rateby the desired time period.

The quantity of sulfur stored on the DOC 30 estimated by the DOC sulfurstorage module 132 and the DOC outlet sulfur 142 (or quantity of sulfurreleased from the DOC) estimated by the DOC sulfur release module 134 isused by the DOC sulfur accumulation module 136 to estimate a totalaccumulation of sulfur on the DOC 30. The DOC sulfur accumulation module136 estimates the total accumulation of sulfur on the DOC 30 based on adifference between the estimated quantity of sulfur stored on the DOC 30and the estimated quantity of sulfur released from the DOC. In oneimplementation, the DOC sulfur accumulation module 136 sets the totalaccumulation of sulfur on the DOC 30 equal to the difference between theestimated quantity of sulfur stored on the DOC 30 and the estimatedquantity of sulfur released from the DOC.

The DOC sulfur regeneration module 138 generates a DOC sulfurregeneration request 140 based on a comparison between the totalaccumulation of sulfur on the DOC 30 estimated by the DOC sulfuraccumulation module 136 and a DOC sulfur accumulation threshold. In oneembodiment, the DOC sulfur regeneration module 138 generates a DOCsulfur regeneration request 140 only when the total accumulation ofsulfur on the DOC 30 estimated by the DOC sulfur accumulation module 136meets (e.g., is equal to or exceeds) the DOC sulfur accumulationthreshold. In such an embodiment, should the total accumulation ofsulfur on the DOC 30 estimated by the DOC sulfur accumulation module 136not meet the DOC sulfur accumulation threshold, then a DOC sulfurregeneration request 140 is not generated. The DOC sulfur regenerationrequest 140 represents a demand to regenerate the DOC 30 at specificregeneration event operating parameters (e.g., exhaust temperature,exhaust mass flow rate, and timing parameter). The operating parametersof the DOC regeneration event demanded by the DOC sulfur regenerationrequest 140 may vary based on any of various factors, such as, forexample, the total accumulation of sulfur on the DOC 30, the period oftime since the last DOC regeneration event, and the like. In someimplementations, the sulfur regeneration request 140 is generated evenif the total accumulation of sulfur on the DOC 30 does not meet the DOCsulfur accumulation threshold. However, in such implementations, therequest 140 may be void of regeneration event parameters, such that therequest effectively does not demand a regeneration event.

The DOC sulfur accumulation threshold corresponds with a DOC performancethreshold. Like described above, the accumulation of sulfur on the DOC30 may have a proportionally negative effect on the performance of theDOC. For example, the greater the accumulation of sulfur on the DOC 30,the lower the oxidation rate of CO to CO₂ and the lower the oxidation ofNO to NO₂. Accordingly, the DOC sulfur accumulation threshold can bepredetermined to correspond with a minimum allowable performancecharacteristic, such as a minimum allowable CO to CO₂ oxidation rate orefficiency and/or minimum allowable NO to NO₂ oxidation rate orefficiency. As defined herein, allowable may mean desirable. In thismanner, the DOC sulfur regeneration module 138 is configured to demand aDOC regeneration event by generating the DOC sulfur regeneration request140 before the performance of the DOC 30 drops below the minimumallowable performance characteristic.

Before a DOC regeneration event according to the DOC sulfur regenerationrequest 140 is initiated, the DOC sulfur regeneration request 140 isreceived by the sulfur regeneration arbitration module 190, whichdetermines whether the DOC sulfur regeneration request has priority overother possible regeneration requests, as will be described in moredetail below. If the sulfur regeneration arbitration module 190determines that the DOC sulfur regeneration request 140 has priority,then the sulfur regeneration arbitration module generates a sulfurregeneration command 112 that corresponds with the regeneration eventparameters demanded by the DOC sulfur regeneration request.

The SCR sulfur module 150 of the sulfur oxidation module 110 isconfigured in a manner analogous to the DOC sulfur module 130 except theSCR sulfur module applies to the SCR catalyst 50 instead of the DOC 30.For example, the SCR sulfur module 150 includes an SCR sulfur storagemodule 152, SCR sulfur release module 154, SCR sulfur accumulationmodule 156, and SCR sulfur regeneration module 158. The SCR sulfurstorage module 152 is configured to estimate the amount of sulfur beingstored on the SCR catalyst 50. According to the illustrated embodiment,the SCR sulfur storage module 152 estimates the amount or quantity ofsulfur being stored on the SCR based on various inputs, such as, forexample, the DOC outlet sulfur 142 estimated by the DOC sulfur releasemodule 134 (i.e., the quantity of sulfur in the exhaust gas exiting theDOC 30 and entering the SCR catalyst 50), the temperature of the SCRcatalyst 50, and the mass flow rate of exhaust gas into the SCRcatalyst. The temperature of the SCR catalyst 50 (e.g., the catalyst bedof the SCR catalyst) can be determined by the SCR sulfur storage module152 according to any of various techniques, such as using estimationmodules and/or physical sensors. For example, the temperature of the SCRcatalyst 50 can be determined based on the difference between exhaustgas temperature measurements taken by the temperature sensors 12upstream and downstream of the SCR catalyst 50. Additionally, oralternatively, the exhaust aftertreatment system 22 may have an SCRcatalyst mid-bed temperature sensor that more directly detects thetemperature of the SCR catalyst 50.

According to one embodiment, the quantity of sulfur being stored on theSCR catalyst 50, which can be expressed as the rate of sulfur beingstored on the SCR catalyst 50, for a given DOC outlet sulfur value 142,can be obtained from a look-up table that is stored on the SCR sulfurstorage module 152 and includes predetermined sulfur storage rates onthe SCR catalyst 50 compared to SCR catalyst temperature values andexhaust mass flow rate values. The SCR sulfur storage module 152 caninclude a plurality of look-up tables each associated with a given DOCoutlet sulfur value 142. Accordingly, once the temperature of the SCRcatalyst 50 and exhaust mass flow rate is determined or known, thesulfur storage rate on the SCR catalyst estimated by the SCR sulfurstorage module 152 is the predetermined value in the look-up table(associated with the determined DOC outlet sulfur value 142) for thedetermined SCR catalyst temperature and exhaust flow rate values. ForDOC outlet sulfur values 142 between or outside those corresponding withthe look-up tables, interpolation or extrapolation techniques can beutilized to estimate the SCR sulfur storage rate.

The quantity of sulfur stored on the SCR catalyst 50 over a desired timeperiod, which can be represented by the time input 192, is thenestimated by the SCR sulfur storage module 152 by multiplying theestimated SCR sulfur storage rate by the desired time period. In certainimplementations, the quantity of sulfur stored on the SCR catalyst 50over the desired time period represents an estimate of the newly storedsulfur on the SCR catalyst, which can be added to a previous estimate ofthe accumulation of sulfur on the SCR catalyst, as will be explained inmore detail below, to obtain a more accurate estimate of the quantity ofsulfur currently stored on the SCR catalyst.

The SCR sulfur release module 154 of the SCR sulfur module 150 isconfigured to estimate the SCR outlet sulfur 162 (i.e., the amount orquantity of sulfur being released from the SCR catalyst 50) based onvarious inputs, such as, for example, the temperature of the SCRcatalyst and the quantity of sulfur stored on the SCR catalyst. The SCRsulfur release module 154 may estimate the temperature of the SCRcatalyst 50 in the same or similar manner as the SCR sulfur storagemodule 152, or simply utilize the temperature of the SCR catalystestimated by the SCR sulfur storage module. Similarly, the quantity ofsulfur stored on the SCR catalyst 50 can be obtained from the SCR sulfurstorage module 152 or can be based on a previous estimate of theaccumulation of sulfur on the SCR catalyst.

According to one embodiment, the SCR outlet sulfur 162 or amount ofsulfur being released from the SCR catalyst 50, which can be expressedas the rate of sulfur being released from the SCR catalyst, can beobtained from a look-up table that is stored on the SCR sulfur releasemodule 154 and includes predetermined sulfur release rates from the SCRcatalyst 50 compared to SCR catalyst temperature values and SCR catalystsulfur storage values. The SCR sulfur release module 154 can include aplurality of look-up tables each associated with a given SCR outletsulfur value 162. Accordingly, once the temperature of the SCR catalyst50 and SCR outlet sulfur value 162 is determined or known, the sulfurrelease rate from the SCR catalyst 50 estimated by the SCR sulfurrelease module 154 is the predetermined value in the look-up table forthe determined SCR temperature and SCR sulfur storage values. Thequantity of sulfur released from the SCR catalyst 50 over a desired timeperiod (e.g., the same desired time period used by the SCR sulfurstorage module 152 to estimate the SCR sulfur storage), which also canbe represented by the time input 192, is then estimated by the SCRsulfur release module 154 by multiplying the estimated SCR sulfurrelease rate by the desired time period.

The quantity of sulfur stored on the SCR catalyst 50 estimated by theSCR sulfur storage module 152 and the SCR outlet sulfur 162 (or quantityof sulfur released from the SCR catalyst) estimated by the SCR sulfurrelease module 154 is used by the SCR sulfur accumulation module 156 toestimate a total accumulation of sulfur on the SCR catalyst 50. The SCRsulfur accumulation module 156 estimates the total accumulation ofsulfur on the SCR catalyst 50 based on a difference between theestimated quantity of sulfur stored on the SCR catalyst 50 and theestimated quantity of sulfur released from the SCR catalyst. In oneimplementation, the SCR sulfur accumulation module 156 sets the totalaccumulation of sulfur on the SCR catalyst 50 equal to the differencebetween the estimated quantity of sulfur stored on the SCR catalyst andthe estimated quantity of sulfur released from the SCR catalyst.

The SCR sulfur regeneration module 158 generates an SCR sulfurregeneration request 160 based on a comparison between the totalaccumulation of sulfur on the SCR catalyst 50 estimated by the SCRsulfur accumulation module 156 and an SCR sulfur accumulation threshold.In one embodiment, the SCR sulfur regeneration module 158 generates anSCR sulfur regeneration request 160 only when the total accumulation ofsulfur on the SCR catalyst 50 estimated by the SCR sulfur accumulationmodule 156 meets (e.g., is equal to or exceeds) the SCR sulfuraccumulation threshold. In such an embodiment, should the totalaccumulation of sulfur on the SCR catalyst 50 estimated by the SCRsulfur accumulation module 156 not meet the SCR sulfur accumulationthreshold, then an SCR sulfur regeneration request 160 is not generated.The SCR sulfur regeneration request 160 represents a demand toregenerate the SCR catalyst 50 at specific regeneration event operatingparameters (e.g., exhaust temperature, exhaust mass flow rate, andtiming parameter). The operating parameters of the SCR catalystregeneration event demanded by the SCR sulfur regeneration request 160may vary based on any of various factors, such as, for example, thetotal accumulation of sulfur on the SCR catalyst 50, the period of timesince the last SCR catalyst regeneration event, and the like. In someimplementations, the sulfur regeneration request 160 is generated evenif the total accumulation of sulfur on the SCR catalyst 50 does not meetthe SCR sulfur accumulation threshold. However, in such implementations,the request 160 may be void of regeneration event parameters, such thatthe request effectively does not demand a regeneration event.

The SCR sulfur accumulation threshold corresponds with an SCR catalystperformance threshold. Like described above, the accumulation of sulfuron the SCR catalyst 50 may have a proportionally negative effect on theperformance of the SCR catalyst. For example, the greater theaccumulation of sulfur on the SCR catalyst 50, the lower the conversionrate of NOx in the presence of ammonia or the lower the NOx conversionefficiency. Accordingly, the SCR sulfur accumulation threshold can bepredetermined to correspond with a minimum allowable performancecharacteristic, such as a minimum allowable NOx conversion rate orefficiency. In this manner, the SCR sulfur regeneration module 158 isconfigured to demand an SCR catalyst regeneration event by generatingthe SCR sulfur regeneration request 160 before the performance of theSCR catalyst 50 drops below the minimum allowable performancecharacteristic. Because the performance characteristics of the DOC 30are different than those of the SCR catalyst 50, the respective sulfuraccumulation thresholds can be different. For example, in certainimplementations, the performance of the DOC 30 may better toleratesulfur accumulations than the SCR catalyst 50. Accordingly, in suchimplementations, the sulfur accumulation threshold of the DOC 30 may behigher than that of the SCR catalyst 50. In AMOX other implementations,the sulfur accumulation threshold of the DOC 30 may be lower than thatof the SCR catalyst 50.

Before an SCR catalyst regeneration event according to the SCR sulfurregeneration request 160 is initiated, the SCR sulfur regenerationrequest is received by the sulfur regeneration arbitration module 190,which determines whether the SCR sulfur regeneration request haspriority over other possible regeneration requests, such as the DOCsulfur regeneration request 140 or other requests as will be describedin more detail below. If the sulfur regeneration arbitration module 190determines that the SCR sulfur regeneration request 160 has priority,then the sulfur regeneration arbitration module generates a sulfurregeneration command 112 that corresponds with the regeneration eventparameters demanded by the SCR sulfur regeneration request.

The AMOX sulfur module 170 of the sulfur oxidation module 110 isconfigured in a manner analogous to the DOC and SCR sulfur modules 130,150 except the AMOX sulfur module applies to the AMOX catalyst 60instead of the DOC 30 and SCR catalyst 50. For example, the AMOX sulfurmodule 170 includes an AMOX sulfur storage module 172, AMOX sulfurrelease module 174, AMOX sulfur accumulation module 176, and AMOX sulfurregeneration module 178. The AMOX sulfur storage module 172 isconfigured to estimate the amount of sulfur being stored on the AMOXcatalyst 60. According to the illustrated embodiment, the AMOX sulfurstorage module 172 estimates the amount or quantity of sulfur beingstored on the AMOX based on various inputs, such as, for example, theSCR outlet sulfur 162 estimated by the SCR sulfur release module 154(i.e., the quantity of sulfur in the exhaust gas exiting the SCRcatalyst 50 and entering the AMOX catalyst 60), the temperature of theAMOX catalyst 60, and the mass flow rate of exhaust gas into the AMOXcatalyst. The temperature of the AMOX catalyst 60 (e.g., the catalystbed of the AMOX catalyst) can be determined by the AMOX sulfur storagemodule 172 according to any of various techniques, such as usingestimation modules and/or physical sensors. For example, the temperatureof the AMOX catalyst 60 can be determined based on the differencebetween exhaust gas temperature measurements taken by the temperaturesensors 12 upstream and downstream of the AMOX catalyst 60.Additionally, or alternatively, the exhaust aftertreatment system 22 mayhave an AMOX catalyst mid-bed temperature sensor that more directlydetects the temperature of the AMOX catalyst 60.

According to one embodiment, the quantity of sulfur being stored on theAMOX catalyst 60, which can be expressed as the rate of sulfur beingstored on the AMOX catalyst, for a given SCR outlet sulfur value 162,can be obtained from a look-up table that is stored on the AMOX sulfurstorage module 172 and includes predetermined sulfur storage rates onthe AMOX catalyst 60 compared to AMOX catalyst temperature values andexhaust mass flow rate values. The AMOX sulfur storage module 172 caninclude a plurality of look-up tables each associated with a given SCRoutlet sulfur value 162. Accordingly, once the temperature of the AMOXcatalyst 60 and exhaust mass flow rate is determined or known, thesulfur storage rate on the AMOX catalyst estimated by the AMOX sulfurstorage module 172 is the predetermined value in the look-up table(associated with the determined SCR outlet sulfur value 162) for thedetermined AMOX catalyst temperature and exhaust flow rate values. ForSCR outlet sulfur values 162 between or outside those corresponding withthe look-up tables, interpolation or extrapolation techniques can beutilized to estimate the AMOX sulfur storage rate.

The quantity of sulfur stored on the AMOX catalyst 60 over a desiredtime period, which can be represented by the time input 192, is thenestimated by the AMOX sulfur storage module 172 by multiplying theestimated AMOX sulfur storage rate by the desired time period. Incertain implementations, the quantity of sulfur stored on the AMOXcatalyst 60 over the desired time period represents an estimate of thenewly stored sulfur on the AMOX catalyst, which can be added to aprevious estimate of the accumulation of sulfur on the AMOX catalyst, aswill be explained in more detail below, to obtain a more accurateestimate of the quantity of sulfur currently stored on the AMOXcatalyst.

The AMOX sulfur release module 174 of the AMOX sulfur module 170 isconfigured to estimate the AMOX outlet sulfur 182 (i.e., the amount orquantity of sulfur being released from the AMOX catalyst 60) based onvarious inputs, such as, for example, the temperature of the AMOXcatalyst and the quantity of sulfur stored on the AMOX catalyst. TheAMOX sulfur release module 174 may estimate the temperature of the AMOXcatalyst 60 in the same or similar manner as the AMOX sulfur storagemodule 172, or simply utilize the temperature of the AMOX catalystestimated by the AMOX sulfur storage module. Similarly, the quantity ofsulfur stored on the AMOX catalyst 60 can be obtained from the AMOXsulfur storage module 172 or can be based on a previous estimate of theaccumulation of sulfur on the AMOX catalyst 60.

According to one embodiment, the AMOX outlet sulfur 182 or amount ofsulfur being released from the AMOX catalyst 60, which can be expressedas the rate of sulfur being released from the AMOX catalyst, can beobtained from a look-up table that is stored on the AMOX sulfur releasemodule 174 and includes predetermined sulfur release rates from the AMOXcatalyst 60 compared to AMOX catalyst temperature values and AMOXcatalyst sulfur storage values. The AMOX sulfur release module 174 caninclude a plurality of look-up tables each associated with a given AMOXoutlet sulfur value 182. Accordingly, once the temperature of the AMOXcatalyst 60 and AMOX outlet sulfur value 182 is determined or known, thesulfur release rate from the AMOX catalyst 60 estimated by the AMOXsulfur release module 174 is the predetermined value in the look-uptable for the determined AMOX temperature and AMOX sulfur storagevalues. The quantity of sulfur released from the AMOX catalyst 60 over adesired time period (e.g., the same desired time period used by the AMOXsulfur storage module 172 to estimate the AMOX sulfur storage), whichalso can be represented by the time input 192, is then estimated by theAMOX sulfur release module 174 by multiplying the estimated AMOX sulfurrelease rate by the desired time period.

The quantity of sulfur stored on the AMOX catalyst 60 estimated by theAMOX sulfur storage module 172 and the AMOX outlet sulfur 182 (orquantity of sulfur released from the AMOX catalyst) estimated by theAMOX sulfur release module 174 is used by the AMOX sulfur accumulationmodule 176 to estimate a total accumulation of sulfur on the AMOXcatalyst 60. The AMOX sulfur accumulation module 176 estimates the totalaccumulation of sulfur on the AMOX catalyst 60 based on a differencebetween the estimated quantity of sulfur stored on the AMOX catalyst 60and the estimated quantity of sulfur released from the AMOX catalyst. Inone implementation, the AMOX sulfur accumulation module 176 sets thetotal accumulation of sulfur on the AMOX catalyst 60 equal to thedifference between the estimated quantity of sulfur stored on the AMOXcatalyst and the estimated quantity of sulfur released from the AMOXcatalyst.

The AMOX sulfur regeneration module 178 generates an AMOX sulfurregeneration request 180 based on a comparison between the totalaccumulation of sulfur on the AMOX catalyst 60 estimated by the AMOXsulfur accumulation module 176 and an AMOX sulfur accumulationthreshold. In one embodiment, the AMOX sulfur regeneration module 178generates an AMOX sulfur regeneration request 180 only when the totalaccumulation of sulfur on the AMOX catalyst 60 estimated by the AMOXsulfur accumulation module 176 meets (e.g., is equal to or exceeds) theAMOX sulfur accumulation threshold. In such an embodiment, should thetotal accumulation of sulfur on the AMOX catalyst 60 estimated by theAMOX sulfur accumulation module 176 not meet the AMOX sulfuraccumulation threshold, then an AMOX sulfur regeneration request 180 isnot generated. The AMOX sulfur regeneration request 180 represents ademand to regenerate the AMOX catalyst 60 at specific regeneration eventoperating parameters (e.g., exhaust temperature, exhaust mass flow rate,and timing parameter). The operating parameters of the AMOX catalystregeneration event demanded by the AMOX sulfur regeneration request 180may vary based on any of various factors, such as, for example, thetotal accumulation of sulfur on the AMOX catalyst 60, the period of timesince the last AMOX catalyst regeneration event, and the like. In someimplementations, the sulfur regeneration request 180 is generated evenif the total accumulation of sulfur on the AMOX catalyst 60 does notmeet the AMOX sulfur accumulation threshold. However, in suchimplementations, the request 180 may be void of regeneration eventparameters, such that the request effectively does not demand aregeneration event.

The AMOX sulfur accumulation threshold corresponds with an AMOX catalystperformance threshold. Like described above, the accumulation of sulfuron the AMOX catalyst 60 may have a proportionally negative effect on theperformance of the AMOX catalyst. For example, the greater theaccumulation of sulfur on the AMOX catalyst 60, the lower the conversionrate of ammonia or the lower the ammonia conversion efficiency.Accordingly, the AMOX sulfur accumulation threshold can be predeterminedto correspond with a minimum allowable performance characteristic, suchas a minimum allowable ammonia oxidation rate or efficiency. In thismanner, the AMOX sulfur regeneration module 178 is configured to demandan AMOX catalyst regeneration event by generating the SCR sulfurregeneration request 180 before the performance of the AMOX catalyst 60drops below the minimum allowable performance characteristic. Becausethe performance characteristics of the DOC 30 and SCR catalyst 50 aredifferent than those of the AMOX catalyst 60, the respective sulfuraccumulation thresholds can be different. For example, in certainimplementations, the performance of the DOC 30 and/or SCR catalyst 50may better tolerate sulfur accumulations than the AMOX catalyst 60.Accordingly, in such implementations, the sulfur accumulation thresholdsof the DOC 30 and/or SCR catalyst 50 may be higher than that of the AMOXcatalyst 60. In other implementations, the sulfur accumulation thresholdof the DOC 30 and/or SCR catalyst 50 may be lower than that of the AMOXcatalyst 60.

Before an AMOX catalyst regeneration event according to the AMOX sulfurregeneration request 180 is initiated, the AMOX sulfur regenerationrequest is received by the sulfur regeneration arbitration module 190,which determines whether the AMOX sulfur regeneration request haspriority over other possible regeneration requests, such as the DOCsulfur regeneration request 140, SCR sulfur regeneration request 160, orother requests as will be described in more detail below. If the sulfurregeneration arbitration module 190 determines that the AMOX sulfurregeneration request 180 has priority, then the sulfur regenerationarbitration module generates a sulfur regeneration command 112 thatcorresponds with the regeneration event parameters demanded by the AMOXsulfur regeneration request.

The sulfur regeneration arbitration module 190 may include a time-basedregeneration module or algorithm configured to request a systemregeneration event of the exhaust aftertreatment system 22 based on thepassing of a preset period of time since the last regeneration event,which may be associated with a predetermined amount of fuel consumed bythe engine 20. Accordingly, the sulfur regeneration module 190 monitorsthe initiation and completion of regeneration events of the exhaustaftertreatment system 22, and monitors the amount of time since thecompletion of the latest regeneration event. The time since the latentregeneration event can be determined from the time input 192, which canbe tied to an internal timer device of the controller 100 or externaltimer device in communication with the controller. When the preset timehas been reached, the time-based regeneration module of the sulfurregeneration arbitration module 190 generates a time-based sulfurregeneration request that demands a regeneration of the exhaustaftertreatment system 22 at specific regeneration event operatingparameters (e.g., exhaust temperature, exhaust mass flow rate, andtiming parameter). The sulfur regeneration arbitration module 190determines whether the time-based sulfur regeneration request haspriority over other possible regeneration requests. If the sulfurregeneration arbitration module 190 determines that the time-basedsulfur regeneration request has priority, then the sulfur regenerationarbitration module generates a sulfur regeneration command 112 thatcorresponds with the regeneration event parameters demanded by thetime-based sulfur regeneration request.

The sulfur regeneration arbitration module 190 may include any ofvarious arbitration schemes for determining which of a plurality ofregeneration requests has priority. Such arbitration schemes may takeinto account precalibrated regeneration timers, system efficiencymonitors, and accumulation thresholds that are set based on the impactof sulfur on the performance and emissions behavior of one or more ofthe aftertreatment components of the system 22. For example, the winningrequest could represent the component that is most severely impacted bysulfur effects if the precalibrated timer has not timed-out and thesystem efficiency is still normal.

The regeneration event parameters demanded by the DOC, SCR, AMOX, andtime-based sulfur regeneration requests can be different. For example,one request may demand a shorter regeneration event that is sufficientto clean sulfur from a corresponding component, but insufficient toclean sulfur from another component. Or, as another example, one requestmay demand a regeneration event with a lower exhaust gas temperaturethat is sufficient to clean sulfur from a corresponding component, butinsufficient to clean sulfur from another component. To account for suchdiscrepancies, the sulfur modules 130, 150, 170 of the sulfur oxidationmodule 110 continue to operate as described above during a regenerationevent to continuously monitor the storage, release, and accumulation ofsulfur on the components while regeneration events are occurring, evenif the regeneration event was triggered for a single component. Forexample, the extra sulfur being released from the DOC 30 during aregeneration event is accounted for in the calculation of the DOC outletsulfur 142 as extra sulfur being introduced into the SCR catalyst 50. Inthis manner, an accurate and current estimate of the sulfur accumulationstatus for each component is known before, during, and after anyregeneration event.

As shown in FIG. 4, the hydrocarbon (HC) oxidation module 120 includes aDOC HC module 230, an SCR HC module 250, an AMOX HC module 270, and a HCregeneration arbitration module 290 each similar to the DOC sulfurmodule 130, an SCR sulfur module 150, an AMOX sulfur module 170, and asulfur regeneration arbitration module 190, but configured for HCaccumulation and removal instead of sulfur accumulation and removal.Each of the DOC HC, SCR HC, and AMOX HC modules 230, 250, 270 generatesa respective HC regeneration request 240, 260, 280 if certain estimatedconditions are met. The HC regeneration requests 240, 260, 280 arereceived by the HC regeneration arbitration module 290, which arbitratesbetween one or more HC regeneration requests, and a timer-basedregeneration request, to generate the HC regeneration command 122. TheHC regeneration command 122 then represents the characteristics of thewinning regeneration request from the arbitration process.

The DOC HC module 230 of the HC oxidation module 120 includes a DOC HCstorage module 232, DOC HC release module 234, DOC HC accumulationmodule 236, and DOC HC regeneration module 238. The DOC HC storagemodule 232 is configured to estimate the amount of HC being stored onthe DOC 30. According to the illustrated embodiment, the DOC HC storagemodule 232 estimates the amount or quantity of HC being stored on theDOC based on various inputs, such as, for example, the engine out HC 224(i.e., the quantity of HC in the exhaust gas exiting the engine 20 andentering the DOC 30). In certain implementations, the engine out HC is afunction of the fuel rate 124 (i.e., the rate of fuel entering and beingconsumed by the engine 20). Generally, the engine out HC can beexpressed in terms of a volumetric or part-per-minute flow rate. Thetemperature of the DOC 30 can be determined in a manner similar to thatdescribed above.

According to one embodiment, the quantity of HC being stored on the DOC30, which can be expressed as the rate of HC being stored on the DOC,for a given engine out HC value 224, can be obtained from a look-uptable that is stored on the DOC HC storage module 232 and includespredetermined HC storage rates on the DOC 30 compared to DOC temperaturevalues and exhaust mass flow rate values. The DOC HC storage module 232can include a plurality of look-up tables each associated with a givenengine out HC value 224. Accordingly, once the temperature of the DOC 30and exhaust mass flow rate is determined or known, the HC storage rateon the DOC estimated by the DOC HC storage module 232 is thepredetermined value in the look-up table (associated with the determinedengine out HC value) for the determined DOC temperature and exhaust flowrate values. Generally, the HC adsorption rate on components is lower athigher exhaust gas temperatures. For engine out HC values between oroutside those corresponding with the look-up tables, interpolation orextrapolation techniques can be utilized to estimate the DOC HC storagerate.

The quantity of HC stored on the DOC 30 over a desired time period,which can be represented by the time input 192, is then estimated by theDOC HC storage module 232 by multiplying the estimated DOC HC storagerate by the desired time period. In certain implementations, thequantity of HC stored on the DOC over the desired time period representsan estimate of the newly stored HC, which can be added to a previousestimate of the accumulation of HC on the DOC 30, as will be explainedin more detail below, to obtain a more accurate estimate of the quantityof HC currently stored on the DOC.

The DOC HC release module 234 of the DOC HC module 230 is configured toestimate the DOC outlet HC 242 (i.e., the amount or quantity of HC beingreleased from the DOC 30) based on various inputs, such as, for example,the temperature of the DOC and the quantity of HC stored on the DOC.Generally, the HC release rate from components is lower at higherexhaust gas temperatures. The DOC HC release module 234 may estimate thetemperature of the DOC 30 in the same or similar manner as the DOC HCstorage module 232, or simply utilize the temperature of the DOCestimated by the DOC HC storage module. Similarly, the quantity of HCstored on the DOC 30 can be obtained from the DOC HC storage module 232or can be based on a previous estimate of the accumulation of HC on theDOC.

According to one embodiment, the DOC outlet HC 242 or amount of HC beingreleased from the DOC 30, which can be expressed as the rate of HC beingreleased from the DOC, can be obtained from a look-up table that isstored on the DOC HC release module 234 and includes predetermined HCrelease rates from the DOC 30 compared to DOC temperature values and DOCHC storage values. The DOC HC release module 234 can include a pluralityof look-up tables each associated with a given DOC outlet HC value.Accordingly, once the temperature of the DOC 30 and DOC outlet HC valueis determined or known, the HC release rate from the DOC estimated bythe DOC HC release module 234 is the predetermined value in the look-uptable for the determined DOC temperature and DOC HC storage values. Thequantity of HC released from the DOC 30 over a desired time period(e.g., the same desired time period used by the DOC HC storage module232 to estimate the DOC HC storage), which also can be represented bythe time input 192, is then estimated by the DOC HC release module 234by multiplying the estimated DOC HC release rate by the desired timeperiod.

The quantity of HC stored on the DOC 30 estimated by the DOC storagemodule 232 and the DOC outlet HC 242 (or quantity of HC released fromthe DOC) estimated by the DOC HC release module 234 is used by the DOCHC accumulation module 236 to estimate a total accumulation of HC on theDOC 30. The DOC HC accumulation module 236 estimates the totalaccumulation of HC on the DOC 30 based on a difference between theestimated quantity of HC stored on the DOC 30 and the estimated quantityof HC released from the DOC. In one implementation, the DOC HCaccumulation module 236 sets the total accumulation of HC on the DOC 30equal to the difference between the estimated quantity of HC stored onthe DOC 30 and the estimated quantity of HC released from the DOC.

The DOC HC regeneration module 238 generates a DOC HC regenerationrequest 240 based on a comparison between the total accumulation of HCon the DOC 30 estimated by the DOC HC accumulation module 236 and a DOCHC accumulation threshold. In one embodiment, the DOC HC regenerationmodule 238 generates a DOC HC regeneration request 240 only when thetotal accumulation of HC on the DOC 30 estimated by the DOC HCaccumulation module 236 meets (e.g., is equal to or exceeds) the DOC HCaccumulation threshold (or other condition thresholds are met). In suchan embodiment, should the total accumulation of HC on the DOC 30estimated by the DOC HC accumulation module 236 not meet the DOC HCaccumulation threshold, then a DOC HC regeneration request 240 is notgenerated. The DOC HC regeneration request 240 represents a demand toregenerate the DOC 30 at specific regeneration event operatingparameters (e.g., exhaust temperature, exhaust mass flow rate, andtiming parameter). The operating parameters of the DOC regenerationevent demanded by the DOC HC regeneration request 240 may vary based onany of various factors, such as, for example, the total accumulation ofHC on the DOC 30, the period of time since the last DOC regenerationevent, and the like. In some implementations, the HC regenerationrequest 240 is generated even if the total accumulation of HC on the DOC30 does not meet the DOC HC accumulation threshold. However, in suchimplementations, the request 140 may be void of regeneration eventparameters, such that the request effectively does not demand aregeneration event.

The DOC HC accumulation threshold corresponds with a DOC performancethreshold. Like described above, the accumulation of HC on the DOC 30may have a proportionally negative effect on the performance of the DOC.For example, the greater the accumulation of HC on the DOC 30, the lowerthe oxidation rate of CO to CO₂ and the lower the oxidation of NO toNO₂. Accordingly, the DOC HC accumulation threshold can be predeterminedto correspond with a minimum allowable performance characteristic, suchas a minimum allowable CO to CO₂ oxidation rate and/or minimum allowableNO to NO₂ oxidation rate. In this manner, the DOC HC regeneration module238 is configured to demand a DOC regeneration event by generating theDOC HC regeneration request 240 before the performance of the DOC 30drops below the minimum allowable performance characteristic.

According to certain embodiments, the DOC HC regeneration module 238 mayinclude an exothermal module 244 that is configured to monitor theexothermal conditions of the DOC 30, which include the heat generationof the DOC. The DOC HC regeneration module 238 compares the exothermalconditions of the DOC 30 against predetermined thresholds and generatesa DOC HC regeneration request 240 when the exothermal conditions meetthe associated thresholds. In one embodiment, an exothermal condition isa heat generation rate of the DOC 30, and an exothermal conditionthreshold is a maximum heat generation rate of the DOC. The maximum heatgeneration rate of the DOC 30 may be associated with a rate above whichan uncontrolled or runaway regeneration of the DOC may occur.Alternatively, the exothermal condition is an amount of heat generatedby the DOC 30, and the exothermal condition threshold is a maximumallowable amount of heat generated by the DOC. The maximum allowableamount of heat generated by the DOC 30 may be associated with a heatgeneration value above which an uncontrolled or runaway regeneration ofthe DOC may occur.

Uncontrolled or runaway regenerations can be mitigated by performing acontrolled regeneration of the DOC 30. Accordingly, the DOC HCregeneration module 238 is configured to generate a DOC HC regenerationrequest 240, which can be considered an exothermal regeneration requestunder such circumstances, demanding a regeneration event when theexothermal condition meets the exothermal condition threshold, or beforean uncontrolled or runaway regeneration event occurs. The parameters ofthe regeneration event demanded by a DOC HC regeneration request 240generated from an exothermal condition threshold being met may bedifferent than a DOC HC regeneration request generated from an estimatedtotal HC accumulation on the DOC meeting a DOC HC accumulationthreshold.

Before a DOC regeneration event according to the DOC HC regenerationrequest 240 is initiated, the DOC HC regeneration request is received bythe HC regeneration arbitration module 290, which determines whether theDOC HC regeneration request has priority over other possibleregeneration requests, as will be described in more detail below. If theHC regeneration arbitration module 290 determines that the DOC HCregeneration request 240 has priority, then the HC regenerationarbitration module generates a HC regeneration command 122 thatcorresponds with the regeneration event parameters demanded by the DOCHC regeneration request.

The SCR HC module 250 of the HC oxidation module 120 is configured in amanner analogous to the DOC HC module 230 except the SCR HC moduleapplies to the SCR catalyst 50 instead of the DOC 30. For example, theSCR HC module 250 includes an SCR HC storage module 252, SCR HC releasemodule 254, SCR HC accumulation module 256, and SCR HC regenerationmodule 258. The SCR HC storage module 252 is configured to estimate theamount of HC being stored on the SCR catalyst 50. According to theillustrated embodiment, the SCR HC storage module 252 estimates theamount or quantity of HC being stored on the SCR based on variousinputs, such as, for example, the DOC outlet HC 242 estimated by the DOCHC release module 234 (i.e., the quantity of HC in the exhaust gasexiting the DOC 30 and entering the SCR catalyst 50), the temperature ofthe SCR catalyst 50, and the mass flow rate of exhaust gas into the SCRcatalyst. The temperature of the SCR catalyst 50 can be determined bythe SCR HC storage module 252 according to any of various techniques asdiscussed above.

According to one embodiment, the quantity of HC being stored on the SCRcatalyst 50, which can be expressed as the rate of HC being stored onthe SCR catalyst 50, for a given DOC outlet HC value 242, can beobtained from a look-up table that is stored on the SCR HC storagemodule 252 and includes predetermined HC storage rates on the SCRcatalyst 50 compared to SCR catalyst temperature values and exhaust massflow rate values. The SCR HC storage module 252 can include a pluralityof look-up tables each associated with a given DOC outlet HC value 242.Accordingly, once the temperature of the SCR catalyst 50 and exhaustmass flow rate is determined or known, the HC storage rate on the SCRcatalyst estimated by the SCR HC storage module 252 is the predeterminedvalue in the look-up table (associated with the determined DOC outlet HCvalue 242) for the determined SCR catalyst temperature and exhaust flowrate values. For DOC outlet HC values 242 between or outside thosecorresponding with the look-up tables, interpolation or extrapolationtechniques can be utilized to estimate the SCR HC storage rate.

The quantity of HC stored on the SCR catalyst 50 over a desired timeperiod, which can be represented by the time input 192, is thenestimated by the SCR HC storage module 252 by multiplying the estimatedSCR HC storage rate by the desired time period. In certainimplementations, the quantity of HC stored on the SCR catalyst 50 overthe desired time period represents an estimate of the newly stored HC onthe SCR catalyst, which can be added to a previous estimate of theaccumulation of HC on the SCR catalyst, as will be explained in moredetail below, to obtain a more accurate estimate of the quantity of HCcurrently stored on the SCR catalyst.

The SCR HC release module 254 of the SCR HC module 250 is configured toestimate the SCR outlet HC 262 (i.e., the amount or quantity of HC beingreleased from the SCR catalyst 50) based on various inputs, such as, forexample, the temperature of the SCR catalyst and the quantity of HCstored on the SCR catalyst. The SCR HC release module 254 may estimatethe temperature of the SCR catalyst 50 in the same or similar manner asthe SCR HC storage module 252, or simply utilize the temperature of theSCR catalyst estimated by the SCR HC storage module. Similarly, thequantity of HC stored on the SCR catalyst 50 can be obtained from theSCR HC storage module 252 or can be based on a previous estimate of theaccumulation of HC on the SCR catalyst.

According to one embodiment, the SCR outlet HC 262 or amount of HC beingreleased from the SCR catalyst 50, which can be expressed as the rate ofHC being released from the SCR catalyst, can be obtained from a look-uptable that is stored on the SCR HC release module 254 and includespredetermined HC release rates from the SCR catalyst 50 compared to SCRcatalyst temperature values and SCR catalyst HC storage values. The SCRHC release module 254 can include a plurality of look-up tables eachassociated with a given SCR outlet HC value 262. Accordingly, once thetemperature of the SCR catalyst 50 and SCR outlet HC value 262 isdetermined or known, the HC release rate from the SCR catalyst 50estimated by the SCR HC release module 254 is the predetermined value inthe look-up table for the determined SCR temperature and SCR HC storagevalues. The quantity of HC released from the SCR catalyst 50 over adesired time period (e.g., the same desired time period used by the SCRHC storage module 252 to estimate the SCR HC storage), which also can berepresented by the time input 192, is then estimated by the SCR HCrelease module 254 by multiplying the estimated SCR HC release rate bythe desired time period.

The quantity of HC stored on the SCR catalyst 50 estimated by the SCR HCstorage module 252 and the SCR outlet HC 262 (or quantity of HC releasedfrom the SCR catalyst) estimated by the SCR HC release module 254 isused by the SCR HC accumulation module 256 to estimate a totalaccumulation of HC on the SCR catalyst 50. The SCR HC accumulationmodule 256 estimates the total accumulation of HC on the SCR catalyst 50based on a difference between the estimated quantity of HC stored on theSCR catalyst 50 and the estimated quantity of HC released from the SCRcatalyst. In one implementation, the SCR HC accumulation module 256 setsthe total accumulation of HC on the SCR catalyst 50 equal to thedifference between the estimated quantity of HC stored on the SCRcatalyst and the estimated quantity of HC released from the SCRcatalyst.

The SCR HC regeneration module 258 generates an SCR HC regenerationrequest 260 based on a comparison between the total accumulation of HCon the SCR catalyst 50 estimated by the SCR HC accumulation module 256and an SCR HC accumulation threshold. In one embodiment, the SCR HCregeneration module 258 generates an SCR HC regeneration request 260only when the total accumulation of HC on the SCR catalyst 50 estimatedby the SCR HC accumulation module 256 meets (e.g., is equal to orexceeds) the SCR HC accumulation threshold. In such an embodiment,should the total accumulation of HC on the SCR catalyst 50 estimated bythe SCR HC accumulation module 256 not meet the SCR HC accumulationthreshold, then an SCR HC regeneration request 260 is not generated. TheSCR HC regeneration request 260 represents a demand to regenerate theSCR catalyst 50 at specific regeneration event operating parameters(e.g., exhaust temperature, exhaust mass flow rate, and timingparameter). The operating parameters of the SCR catalyst regenerationevent demanded by the SCR HC regeneration request 260 may vary based onany of various factors, such as, for example, the total accumulation ofHC on the SCR catalyst 50, the period of time since the last SCRcatalyst regeneration event, and the like. In some implementations, theHC regeneration request 260 is generated even if the total accumulationof HC on the SCR catalyst 50 does not meet the SCR HC accumulationthreshold. However, in such implementations, the request 260 may be voidof regeneration event parameters, such that the request effectively doesnot demand a regeneration event.

The SCR HC accumulation threshold corresponds with an SCR catalystperformance threshold. Like described above, the accumulation of HC onthe SCR catalyst 50 may have a proportionally negative effect on theperformance of the SCR catalyst. For example, the greater theaccumulation of HC on the SCR catalyst 50, the lower the conversion rateof NOx in the presence of ammonia or the lower the NOx conversionefficiency. Accordingly, the SCR HC accumulation threshold can bepredetermined to correspond with a minimum allowable performancecharacteristic, such as a minimum allowable NOx conversion rate orefficiency. In this manner, the SCR HC regeneration module 258 isconfigured to demand an SCR catalyst regeneration event by generatingthe SCR HC regeneration request 260 before the performance of the SCRcatalyst 50 drops below the minimum allowable performancecharacteristic. Because the performance characteristics of the DOC 30are different than those of the SCR catalyst 50, the respective HCaccumulation thresholds can be different. For example, in certainimplementations, the performance of the DOC 30 may better tolerate HCaccumulations than the SCR catalyst 50. Accordingly, in suchimplementations, the HC accumulation threshold of the DOC 30 may behigher than that of the SCR catalyst 50. In AMOX other implementations,the HC accumulation threshold of the DOC 30 may be lower than that ofthe SCR catalyst 50.

Before an SCR catalyst regeneration event according to the SCR HCregeneration request 260 is initiated, the SCR HC regeneration requestis received by the HC regeneration arbitration module 290, whichdetermines whether the SCR HC regeneration request has priority overother possible regeneration requests, such as the DOC HC regenerationrequest 240 or other requests as will be described in more detail below.If the HC regeneration arbitration module 290 determines that the SCR HCregeneration request 260 has priority, then the HC regenerationarbitration module generates a HC regeneration command 122 thatcorresponds with the regeneration event parameters demanded by the SCRHC regeneration request.

The AMOX HC module 270 of the HC oxidation module 120 is configured in amanner analogous to the DOC and SCR HC modules 230, 250 except the AMOXHC module applies to the AMOX catalyst 60 instead of the DOC 30 and SCRcatalyst 50. For example, the AMOX HC module 270 includes an AMOX HCstorage module 272, AMOX HC release module 274, AMOX HC accumulationmodule 276, and AMOX HC regeneration module 278. The AMOX HC storagemodule 272 is configured to estimate the amount of HC being stored onthe AMOX catalyst 60. According to the illustrated embodiment, the AMOXHC storage module 272 estimates the amount or quantity of HC beingstored on the AMOX based on various inputs, such as, for example, theSCR outlet HC 262 estimated by the SCR HC release module 254 (i.e., thequantity of HC in the exhaust gas exiting the SCR catalyst 50 andentering the AMOX catalyst 60), the temperature of the AMOX catalyst 60,and the mass flow rate of exhaust gas into the AMOX catalyst. Thetemperature of the AMOX catalyst 60 (e.g., the catalyst bed of the AMOXcatalyst) can be determined by the AMOX HC storage module 272 accordingto any of various techniques, such as using estimation modules and/orphysical sensors. For example, the temperature of the AMOX catalyst 60can be determined based on the difference between exhaust gastemperature measurements taken by the temperature sensors 12 upstreamand downstream of the AMOX catalyst 60. Additionally, or alternatively,the exhaust aftertreatment system 22 may have an AMOX catalyst mid-bedtemperature sensor that more directly detects the temperature of theAMOX catalyst 60.

According to one embodiment, the quantity of HC being stored on the AMOXcatalyst 60, which can be expressed as the rate of HC being stored onthe AMOX catalyst, for a given SCR outlet HC value 262, can be obtainedfrom a look-up table that is stored on the AMOX HC storage module 272and includes predetermined HC storage rates on the AMOX catalyst 60compared to AMOX catalyst temperature values and exhaust mass flow ratevalues. The AMOX HC storage module 272 can include a plurality oflook-up tables each associated with a given SCR outlet HC value 262.Accordingly, once the temperature of the AMOX catalyst 60 and exhaustmass flow rate is determined or known, the HC storage rate on the AMOXcatalyst estimated by the AMOX HC storage module 272 is thepredetermined value in the look-up table (associated with the determinedSCR outlet HC value 262) for the determined AMOX catalyst temperatureand exhaust flow rate values. For SCR outlet HC values 262 between oroutside those corresponding with the look-up tables, interpolation orextrapolation techniques can be utilized to estimate the AMOX HC storagerate.

The quantity of HC stored on the AMOX catalyst 60 over a desired timeperiod, which can be represented by the time input 192, is thenestimated by the AMOX HC storage module 272 by multiplying the estimatedAMOX HC storage rate by the desired time period. In certainimplementations, the quantity of HC stored on the AMOX catalyst 60 overthe desired time period represents an estimate of the newly stored HC onthe AMOX catalyst, which can be added to a previous estimate of theaccumulation of HC on the AMOX catalyst, as will be explained in moredetail below, to obtain a more accurate estimate of the quantity of HCcurrently stored on the AMOX catalyst.

The AMOX HC release module 274 of the AMOX HC module 270 is configuredto estimate the AMOX outlet HC 282 (i.e., the amount or quantity of HCbeing released from the AMOX catalyst 60) based on various inputs, suchas, for example, the temperature of the AMOX catalyst and the quantityof HC stored on the AMOX catalyst. The AMOX HC release module 274 mayestimate the temperature of the AMOX catalyst 60 in the same or similarmanner as the AMOX HC storage module 272, or simply utilize thetemperature of the AMOX catalyst estimated by the AMOX HC storagemodule. Similarly, the quantity of HC stored on the AMOX catalyst 60 canbe obtained from the AMOX HC storage module 272 or can be based on aprevious estimate of the accumulation of HC on the AMOX catalyst 60.

According to one embodiment, the AMOX outlet HC 282 or amount of HCbeing released from the AMOX catalyst 60, which can be expressed as therate of HC being released from the AMOX catalyst, can be obtained from alook-up table that is stored on the AMOX HC release module 274 andincludes predetermined HC release rates from the AMOX catalyst 60compared to AMOX catalyst temperature values and AMOX catalyst HCstorage values. The AMOX HC release module 274 can include a pluralityof look-up tables each associated with a given AMOX outlet HC value 282.Accordingly, once the temperature of the AMOX catalyst 60 and AMOXoutlet HC value 282 is determined or known, the HC release rate from theAMOX catalyst 60 estimated by the AMOX HC release module 274 is thepredetermined value in the look-up table for the determined AMOXtemperature and AMOX HC storage values. The quantity of HC released fromthe AMOX catalyst 60 over a desired time period (e.g., the same desiredtime period used by the AMOX HC storage module 272 to estimate the AMOXHC storage), which also can be represented by the time input 192, isthen estimated by the AMOX HC release module 274 by multiplying theestimated AMOX HC release rate by the desired time period.

The quantity of HC stored on the AMOX catalyst 60 estimated by the AMOXHC storage module 272 and the AMOX outlet HC 282 (or quantity of HCreleased from the AMOX catalyst) estimated by the AMOX HC release module274 is used by the AMOX HC accumulation module 276 to estimate a totalaccumulation of HC on the AMOX catalyst 60. The AMOX HC accumulationmodule 276 estimates the total accumulation of HC on the AMOX catalyst60 based on a difference between the estimated quantity of HC stored onthe AMOX catalyst 60 and the estimated quantity of HC released from theAMOX catalyst. In one implementation, the AMOX HC accumulation module276 sets the total accumulation of HC on the AMOX catalyst 60 equal tothe difference between the estimated quantity of HC stored on the AMOXcatalyst and the estimated quantity of HC released from the AMOXcatalyst.

The AMOX HC regeneration module 278 generates an AMOX HC regenerationrequest 280 based on a comparison between the total accumulation of HCon the AMOX catalyst 60 estimated by the AMOX HC accumulation module 276and an AMOX HC accumulation threshold. In one embodiment, the AMOX HCregeneration module 278 generates an AMOX HC regeneration request 280only when the total accumulation of HC on the AMOX catalyst 60 estimatedby the AMOX HC accumulation module 276 meets (e.g., is equal to orexceeds) the AMOX HC accumulation threshold. In such an embodiment,should the total accumulation of HC on the AMOX catalyst 60 estimated bythe AMOX HC accumulation module 276 not meet the AMOX HC accumulationthreshold, then an AMOX HC regeneration request 280 is not generated.The AMOX HC regeneration request 280 represents a demand to regeneratethe AMOX catalyst 60 at specific regeneration event operating parameters(e.g., exhaust temperature, exhaust mass flow rate, and timingparameter). The operating parameters of the AMOX catalyst regenerationevent demanded by the AMOX HC regeneration request 280 may vary based onany of various factors, such as, for example, the total accumulation ofHC on the AMOX catalyst 60, the period of time since the last AMOXcatalyst regeneration event, and the like. In some implementations, theHC regeneration request 280 is generated even if the total accumulationof HC on the AMOX catalyst 60 does not meet the AMOX HC accumulationthreshold. However, in such implementations, the request 280 may be voidof regeneration event parameters, such that the request effectively doesnot demand a regeneration event.

The AMOX HC accumulation threshold corresponds with an AMOX catalystperformance threshold. Like described above, the accumulation of HC onthe AMOX catalyst 60 may have a proportionally negative effect on theperformance of the AMOX catalyst. For example, the greater theaccumulation of HC on the AMOX catalyst 60, the lower the conversionrate of ammonia or the lower the ammonia conversion efficiency.Accordingly, the AMOX HC accumulation threshold can be predetermined tocorrespond with a minimum allowable performance characteristic, such asa minimum allowable ammonia conversion rate or efficiency. In thismanner, the AMOX HC regeneration module 278 is configured to demand anAMOX catalyst regeneration event by generating the SCR HC regenerationrequest 260 before the performance of the AMOX catalyst 60 drops belowthe minimum allowable performance characteristic. Because theperformance characteristics of the DOC 30 and SCR catalyst 50 aredifferent than those of the AMOX catalyst 60, the respective HCaccumulation thresholds can be different. For example, in certainimplementations, the performance of the DOC 30 and/or SCR catalyst 50may better tolerate HC accumulations than the AMOX catalyst 60.Accordingly, in such implementations, the HC accumulation thresholds ofthe DOC 30 and/or SCR catalyst 50 may be higher than that of the AMOXcatalyst 60. In other implementations, the HC accumulation threshold ofthe DOC 30 and/or SCR catalyst 50 may be lower than that of the AMOXcatalyst 60.

According to certain embodiments, the AMOX HC regeneration module 278may include an exothermal module 280 that is configured to monitor theexothermal conditions of the AMOX catalyst 60, which include the heatgeneration of the AMOX catalyst. The AMOX HC regeneration module 278compares the exothermal conditions of the AMOX catalyst 60 againstpredetermined thresholds and generates an AMOX HC regeneration request280 when the exothermal conditions meet the associated thresholds. Inone embodiment, an exothermal condition is a heat generation rate of theAMOX catalyst 60, and an exothermal condition threshold is a maximumheat generation rate of the AMOX catalyst. The maximum heat generationrate of the AMOX catalyst 60 may be associated with a rate above whichan uncontrolled or runaway regeneration of the AMOX catalyst may occur.Alternatively, the exothermal condition is an amount of heat generatedby the AMOX catalyst 60, and the exothermal condition threshold is amaximum allowable amount of heat generated by the AMOX catalyst. Themaximum allowable amount of heat generated by the DOC 30 may beassociated with a heat generation value above which an uncontrolled orrunaway regeneration of the DOC may occur. Uncontrolled or runawayregenerations can be mitigated by performing a controlled regenerationof the AMOX catalyst 60. Accordingly, the AMOX HC regeneration module278 is configured to generate an AMOX HC regeneration request 280demanding a regeneration event when the exothermal condition meets theexothermal condition threshold, or before an uncontrolled or runawayregeneration event occurs. The parameters of the regeneration eventdemanded by an AMOX HC regeneration request 280 generated from anexothermal condition threshold being met may be different than an AMOXHC regeneration request generated from an estimated total HCaccumulation on the AMOX catalyst meeting an AMOX HC accumulationthreshold.

Before an AMOX catalyst regeneration event according to the AMOX HCregeneration request 280 is initiated, the AMOX HC regeneration requestis received by the HC regeneration arbitration module 290, whichdetermines whether the AMOX HC regeneration request has priority overother possible regeneration requests, such as the DOC HC regenerationrequest 240, SCR HC regeneration request 260, or other requests as willbe described in more detail below. If the HC regeneration arbitrationmodule 290 determines that the AMOX HC regeneration request 280 haspriority, then the HC regeneration arbitration module generates a HCregeneration command 122 that corresponds with the regeneration eventparameters demanded by the AMOX HC regeneration request.

The HC regeneration arbitration module 290 may include a time-basedregeneration module or algorithm configured to request a regenerationevent of the exhaust aftertreatment system 22 based on the passing of apreset period of time since the last regeneration event, which may beassociated with a predetermined amount of fuel consumed by the engine20. Accordingly, the HC regeneration module 290 monitors the initiationand completion of regeneration events of the exhaust aftertreatmentsystem 22, and monitors the amount of time since the completion of thelatest regeneration event. The time since the latent regeneration eventcan be determined from the time input 292, which can be tied to aninternal timer device of the controller 100 or external timer device incommunication with the controller. When the preset time has beenreached, the time-based regeneration module of the HC regenerationarbitration module 290 generates a time-based HC regeneration requestthat demands a regeneration of the exhaust aftertreatment system 22 atspecific regeneration event operating parameters (e.g., exhausttemperature, exhaust mass flow rate, and timing parameter). The HCregeneration arbitration module 290 determines whether the time-based HCregeneration request has priority over other possible regenerationrequests. If the HC regeneration arbitration module 290 determines thatthe time-based HC regeneration request has priority, then the HCregeneration arbitration module generates a HC regeneration command 122that corresponds with the regeneration event parameters demanded by thetime-based HC regeneration request.

The HC regeneration arbitration module 290 may include any of variousarbitration schemes for determining which of a plurality of regenerationrequests has priority. Such arbitration schemes may take into accountprecalibrated regeneration timers, system efficiency monitors, andaccumulation thresholds that are set based on the impact of HC on theperformance and emissions behavior of one or more of the aftertreatmentcomponents of the system 22. For example, the winning request couldrepresent the component that is most severely impacted by HC effects ifthe precalibrated timer has not timed-out and the system efficiency isstill normal.

The regeneration event parameters demanded by the DOC, SCR, AMOX, andtime-based HC regeneration requests can be different. For example, onerequest may demand a shorter regeneration event that is sufficient toclean HC from a corresponding component, but insufficient to clean HCfrom another component. Or, as another example, one request may demand aregeneration event with a lower exhaust gas temperature that issufficient to clean HC from a corresponding component, but insufficientto clean HC from another component. To account for such discrepancies,the HC modules 230, 250, 270 of the HC oxidation module 120 continue tooperate as described above during a regeneration event to continuouslymonitor the storage, release, and accumulation of HC on the componentswhile regeneration events are occurring, even if the regeneration eventwas triggered for a single component. For example, the extra HC beingreleased from the DOC 30 during a regeneration event is accounted for inthe calculation of the DOC outlet HC 242 as extra HC being introducedinto the SCR catalyst 50. In this manner, an accurate and currentestimate of the HC accumulation status for each component is knownbefore, during, and after any regeneration event.

In certain embodiments of a controller 100 having both a sulfuroxidation module 110 and hydrocarbon oxidation module 120, the sulfurand HC regeneration arbitration modules 190, 290 may be combined to forma single arbitration module. The single arbitration module would beconfigured to arbitrate between sulfur regeneration requests and HCregeneration requests to determine which of multiple requests haspriority.

Although not shown, the controller 100 can include other poisonoxidation modules configured analogously to the sulfur and HC oxidationmodules 110, 120 to estimate poison accumulation levels on thecomponents of the exhaust aftertreatment system 22 and requestregeneration events if the poison accumulation levels reachcorresponding predetermined thresholds. For example, the controller 100can include a water oxidation module that estimate water accumulationlevels on the components of the exhaust aftertreatment system 22 andrequests regenerations event if the water accumulation levels reachcorresponding predetermined water accumulation thresholds. Other poisonscan include platinum (or other precious metals migrated from the DOC 30to the SCR catalyst 50, alkali salts (e.g., Na and K from contaminatedurea solutions), and phosphorus and zinc from lubrication oil.Additionally, the thermal degradation of a catalyst, which ischaracterized by the progressive loss of reaction sites, can beconsidered a type of poison applicable to the present disclosure.

Additionally, although not shown, for embodiments with exhaustaftertreatment systems 22 that include a DPF 40, each of the sulfur andhydrocarbon oxidation modules 110, 120 of the controller 100 can includea DPF sulfur and HC module, respectively. In such embodiments, the DPFsulfur and HC modules are configured in a manner analogous to the DOC,SCR, and AMOX sulfur modules 130, 150, 170, and the SCR HC module 250,respectively, except the DPF sulfur and HC modules apply to thecondition and regeneration of the DPF 40.

Referring to FIG. 5, a method 300 for separately estimating conditionsof aftertreatment system components and regenerating the components isshown. In certain implementations, the steps of the method 300 may beexecuted by the modules of the controller 100 described above.

The method 300 begins by estimating the quantity of a poison accumulatedon a DOC at 310. If the poison accumulation on the DOC is above or atleast meets an associated threshold at 320, then the method 300 commandsa regeneration of the DOC at 380, which at least partially regeneratesother components of the aftertreatment system. However, if the poisonaccumulation on the DOC is below or does not meet the associatedthreshold at 320, then the method 300 proceeds to estimate the quantityof a poison accumulated on an SCR catalyst at 330. If the poisonaccumulation on the SCR catalyst is above or at least meets anassociated threshold at 340, then the method 300 commands a regenerationof the SCR catalyst at 380, which at least partially regenerates othercomponents of the aftertreatment system. However, if the poisonaccumulation on the SCR catalyst is below or does not meet theassociated threshold at 340, then the method 300 proceeds to estimatethe quantity of a poison accumulated on an AMOX catalyst at 350. If thepoison accumulation on the AMOX catalyst is above or at least meets anassociated threshold at 360, then the method 300 commands a regenerationof the AMOX catalyst at 380, which at least partially regenerates othercomponents of the aftertreatment system. However, if the poisonaccumulation on the AMOX catalyst is below or does not meet theassociated threshold at 360, then the method 300 proceeds to determineif a predetermined period of time has passed since a previousregeneration event at 370. If the predetermined period of time haspassed at 370, then the method 300 commands a regeneration of thecomponents of the aftertreatment system. However, if the predeterminedperiod of time has not passed at 370, then the method 300 does notcommand a regeneration event and ends.

In certain implementations, the poison of the method 300 can be one orboth of sulfur and HC. In some implementations, the poison of the method300 can be water. According to some embodiments, the estimation of theaccumulation of the poison on the SCR catalyst at 330 is at leastindirectly dependent on the estimate of the accumulation of the poisonon the DOC Likewise, the estimation of the accumulation of the poison onthe AMOX catalyst at 370 can be at least indirectly dependent on theestimate of the accumulation of the poison on the SCR catalyst. Also, insome embodiments, the estimation of the poison accumulation on the DOC,SCR catalyst, and AMOX catalyst includes estimations of the amount ofpoison being stored and the amount of poison being released from theDOC, SCR catalyst, and AMOX catalyst, respectively. Although not shown,in some implementations, the method 300 may include estimating anexothermic condition for each of the DOC and AMOX catalysts, and commanda regeneration event at 380 if the exothermic condition for the DOC andAMOX catalysts meet an associated threshold.

The schematic flow chart diagrams and method schematic diagramsdescribed above are generally set forth as logical flow chart diagrams.As such, the depicted order and labeled steps are indicative ofrepresentative embodiments. Other steps, orderings and methods may beconceived that are equivalent in function, logic, or effect to one ormore steps, or portions thereof, of the methods illustrated in theschematic diagrams.

Additionally, the format and symbols employed are provided to explainthe logical steps of the schematic diagrams and are understood not tolimit the scope of the methods illustrated by the diagrams. Althoughvarious arrow types and line types may be employed in the schematicdiagrams, they are understood not to limit the scope of thecorresponding methods. Indeed, some arrows or other connectors may beused to indicate only the logical flow of a method. For instance, anarrow may indicate a waiting or monitoring period of unspecifiedduration between enumerated steps of a depicted method. Additionally,the order in which a particular method occurs may or may not strictlyadhere to the order of the corresponding steps shown. It will also benoted that each block of the block diagrams and/or flowchart diagrams,and combinations of blocks in the block diagrams and/or flowchartdiagrams, can be implemented by special purpose hardware-based systemsthat perform the specified functions or acts, or combinations of specialpurpose hardware and program code.

Many of the functional units described in this specification have beenlabeled as modules, in order to more particularly emphasize theirimplementation independence. For example, a module may be implemented asa hardware circuit comprising custom VLSI circuits or gate arrays,off-the-shelf semiconductors such as logic chips, transistors, or otherdiscrete components. A module may also be implemented in programmablehardware devices such as field programmable gate arrays, programmablearray logic, programmable logic devices or the like.

Modules may also be implemented in software for execution by varioustypes of processors. An identified module of executable code may, forinstance, comprise one or more physical or logical blocks of computerinstructions, which may, for instance, be organized as an object,procedure, or function. Nevertheless, the executables of an identifiedmodule need not be physically located together, but may comprisedisparate instructions stored in different locations which, when joinedlogically together, comprise the module and achieve the stated purposefor the module.

Indeed, a module of computer readable program code may be a singleinstruction, or many instructions, and may even be distributed overseveral different code segments, among different programs, and acrossseveral memory devices. Similarly, operational data may be identifiedand illustrated herein within modules, and may be embodied in anysuitable form and organized within any suitable type of data structure.The operational data may be collected as a single data set, or may bedistributed over different locations including over different storagedevices, and may exist, at least partially, merely as electronic signalson a system or network. Where a module or portions of a module areimplemented in software, the computer readable program code may bestored and/or propagated on in one or more computer readable medium(s).

The computer readable medium may be a tangible computer readable storagemedium storing the computer readable program code. The computer readablestorage medium may be, for example, but not limited to, an electronic,magnetic, optical, electromagnetic, infrared, holographic,micromechanical, or semiconductor system, apparatus, or device, or anysuitable combination of the foregoing.

More specific examples of the computer readable medium may include butare not limited to a portable computer diskette, a hard disk, a randomaccess memory (RAM), a read-only memory (ROM), an erasable programmableread-only memory (EPROM or Flash memory), a portable compact discread-only memory (CD-ROM), a digital versatile disc (DVD), an opticalstorage device, a magnetic storage device, a holographic storage medium,a micromechanical storage device, or any suitable combination of theforegoing. In the context of this document, a computer readable storagemedium may be any tangible medium that can contain, and/or storecomputer readable program code for use by and/or in connection with aninstruction execution system, apparatus, or device.

The computer readable medium may also be a computer readable signalmedium. A computer readable signal medium may include a propagated datasignal with computer readable program code embodied therein, forexample, in baseband or as part of a carrier wave. Such a propagatedsignal may take any of a variety of forms, including, but not limitedto, electrical, electro-magnetic, magnetic, optical, or any suitablecombination thereof. A computer readable signal medium may be anycomputer readable medium that is not a computer readable storage mediumand that can communicate, propagate, or transport computer readableprogram code for use by or in connection with an instruction executionsystem, apparatus, or device. Computer readable program code embodied ona computer readable signal medium may be transmitted using anyappropriate medium, including but not limited to wireless, wireline,optical fiber cable, Radio Frequency (RF), or the like, or any suitablecombination of the foregoing

In one embodiment, the computer readable medium may comprise acombination of one or more computer readable storage mediums and one ormore computer readable signal mediums. For example, computer readableprogram code may be both propagated as an electro-magnetic signalthrough a fiber optic cable for execution by a processor and stored onRAM storage device for execution by the processor.

Computer readable program code for carrying out operations for aspectsof the present invention may be written in any combination of one ormore programming languages, including an object oriented programminglanguage such as Java, Smalltalk, C++ or the like and conventionalprocedural programming languages, such as the “C” programming languageor similar programming languages. The computer readable program code mayexecute entirely on the user's computer, partly on the user's computer,as a stand-alone software package, partly on the user's computer andpartly on a remote computer or entirely on the remote computer orserver. In the latter scenario, the remote computer may be connected tothe user's computer through any type of network, including a local areanetwork (LAN) or a wide area network (WAN), or the connection may bemade to an external computer (for example, through the Internet using anInternet Service Provider).

The program code may also be stored in a computer readable medium thatcan direct a computer, other programmable data processing apparatus, orother devices to function in a particular manner, such that theinstructions stored in the computer readable medium produce an articleof manufacture including instructions which implement the function/actspecified in the schematic flowchart diagrams and/or schematic blockdiagrams block or blocks.

The program code may also be loaded onto a computer, other programmabledata processing apparatus, or other devices to cause a series ofoperational steps to be performed on the computer, other programmableapparatus or other devices to produce a computer implemented processsuch that the program code which executed on the computer or otherprogrammable apparatus provide processes for implementing thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

Reference throughout this specification to “one embodiment,” “anembodiment,” or similar language means that a particular feature,structure, or characteristic described in connection with the embodimentis included in at least one embodiment of the present invention. Thus,appearances of the phrases “in one embodiment,” “in an embodiment,” andsimilar language throughout this specification may, but do notnecessarily, all refer to the same embodiment. Similarly, the use of theterm “implementation” means an implementation having a particularfeature, structure, or characteristic described in connection with oneor more embodiments of the present disclosure, however, absent anexpress correlation to indicate otherwise, an implementation may beassociated with one or more embodiments.

The present disclosure may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. The describedembodiments are to be considered in all respects only as illustrativeand not restrictive. The scope of the disclosure is, therefore,indicated by the appended claims rather than by the foregoingdescription. All changes which come within the meaning and range ofequivalency of the claims are to be embraced within their scope.

What is claimed is:
 1. An apparatus for an exhaust aftertreatmentsystem, comprising: a first aftertreatment component poison moduleconfigured to generate a first component poison regeneration requestbased on an estimated accumulation of a first poison on the firstaftertreatment component, the accumulation of the first poison on thefirst aftertreatment component being based on an estimated amount of thefirst poison being released from the first aftertreatment component; anda second aftertreatment component poison module configured to generate asecond component poison regeneration request based on an estimatedaccumulation of the first poison on the second aftertreatment component,the accumulation of the first poison on the second aftertreatmentcomponent being based on the estimated amount of the first poison beingreleased from the first aftertreatment component.
 2. The apparatus ofclaim 1, further comprising a poison regeneration arbitration moduleconfigured to generate a poison regeneration command based on anarbitration of the first and second component poison regenerationrequests.
 3. The apparatus of claim 2, further comprising a time-basedregeneration module configured to generate a system regeneration requestbased on a passage of a preset period of time, wherein the poisonregeneration arbitration module is configured to generate the poisonregeneration command based on an arbitration of the first componentpoison regeneration request, second component poison regenerationrequest, and system regeneration request.
 4. The apparatus of claim 1,wherein the accumulation of the first poison on the secondaftertreatment component is based on an estimated amount of the firstpoison being released from the second aftertreatment component, theapparatus further comprising a third aftertreatment component poisonmodule configured to generate a third component poison regenerationrequest based on an estimated accumulation of the first poison on thethird aftertreatment component, the accumulation of the first poison onthe third aftertreatment component being based on the estimated amountof the first poison being released from the second aftertreatmentcomponent.
 5. The apparatus of claim 1, wherein: the firstaftertreatment component poison module is configured to estimate anamount of the first poison being stored on the first aftertreatmentcomponent, wherein the accumulation of the first poison on the firstaftertreatment component is based on a difference between the amount ofthe first poison being stored on the first aftertreatment component andthe amount of the first poison being released from the firstaftertreatment component; and the second aftertreatment component poisonmodule is configured to estimate an amount of the first poison beingstored on the second aftertreatment component, wherein the accumulationof the first poison on the second aftertreatment component is based on adifference between the amount of the first poison being stored on thesecond aftertreatment component and the amount of the first poison beingreleased from the second aftertreatment component.
 6. The apparatus ofclaim 5, wherein: the amount of the first poison being stored on thefirst aftertreatment component is estimated based on a temperature ofthe first aftertreatment component and a mass flow rate of exhaust gasinto the first aftertreatment component; and the amount of the firstpoison being stored on the second aftertreatment component is estimatedbased on a temperature of the second aftertreatment component and a massflow rate of exhaust gas into the second aftertreatment component. 7.The apparatus of claim 6, wherein: the amount of the first poison beingreleased from the first aftertreatment component is estimated based onthe temperature of the first aftertreatment component and the amount ofthe first poison being stored on the first aftertreatment component; andthe amount of the first poison being released from the secondaftertreatment component is estimated based on the temperature of thesecond aftertreatment component and the amount of the first poison beingstored on the second aftertreatment component.
 8. The apparatus of claim1, wherein the first component poison regeneration request comprisesfirst regeneration event parameters and the second component poisonregeneration request comprises second regeneration event parameters,wherein the first regeneration event parameters are different than thesecond regeneration event parameters.
 9. The apparatus of claim 1,wherein the first poison comprises one of sulfur, hydrocarbon, or water.10. The apparatus of claim 1, wherein: the first aftertreatmentcomponent comprises one of a diesel oxidation catalyst, a dieselparticulate filter, a selective catalytic reduction catalyst, or anammonia oxidation catalyst; and the second aftertreatment componentcomprises another one of the diesel oxidation catalyst, dieselparticulate filter, selective catalytic reduction catalyst, or ammoniaoxidation catalyst.
 11. The apparatus of claim 1, further comprising: athird aftertreatment component poison module configured to generate athird component poison regeneration request based on an estimatedaccumulation of a second poison on the first aftertreatment component,the accumulation of the second poison on the first aftertreatmentcomponent being based on an amount of the second poison being releasedfrom the first aftertreatment component; and a fourth aftertreatmentcomponent poison module configured to generate a fourth component poisonregeneration request based on an estimated accumulation of the secondpoison on the second aftertreatment component, the accumulation of thesecond poison on the second aftertreatment component being based on theestimated amount of the second poison being released from the firstaftertreatment component.
 12. The apparatus of claim 2, wherein thepoison regeneration arbitration module is further configured to generatethe poison regeneration command based on an arbitration of the first,second, third, and fourth component poison regeneration requests. 13.The apparatus of claim 1, wherein: the first aftertreatment componentpoison module generates the first component poison regeneration requestwhen the estimated accumulation of the first poison on the firstaftertreatment component meets a first poison accumulation threshold,the first poison accumulation threshold corresponding with a minimumallowable performance characteristic of the first aftertreatmentcomponent; and the second aftertreatment component poison modulegenerates the second component poison regeneration request when theestimated accumulation of the first poison on the second aftertreatmentcomponent meets a second poison accumulation threshold, the secondpoison accumulation threshold corresponding with a minimum allowableperformance characteristic of the second aftertreatment component. 14.The apparatus of claim 13, wherein the first poison accumulationthreshold is different than the second poison accumulation threshold.15. The apparatus of claim 13, wherein: the first aftertreatmentcomponent comprises one of a diesel oxidation catalyst, a selectivecatalytic reduction catalyst, or an ammonia oxidation catalyst, and theminimum allowable performance characteristic of the first aftertreatmentcomponent comprises one of a minimum allowable NO to NO₂ oxidationefficiency, a minimum allowable NOx conversion efficiency, or a minimumallowable ammonia oxidation efficiency, respectively; and the secondaftertreatment component comprises another one of the diesel oxidationcatalyst, selective catalytic reduction catalyst, or ammonia oxidationcatalyst, and the minimum allowable performance characteristic of thesecond aftertreatment component comprises one of the minimum allowableNO to NO₂ oxidation efficiency, minimum allowable NOx conversionefficiency, or minimum allowable ammonia oxidation efficiency,respectively
 16. The apparatus of claim 1, wherein the first poisoncomprises hydrocarbon, and wherein at least the first aftertreatmentcomponent poison module comprises an exothermal module configured tomonitor an exothermal condition of the first aftertreatment component,and wherein the first aftertreatment component poison module generatesan exothermal regeneration request when the exothermal condition meetsan exothermal condition threshold.
 17. An exhaust aftertreatment systemin exhaust gas receiving communication with an internal combustionengine, comprising: a diesel oxidation catalyst (DOC); a selectivecatalytic reduction (SCR) catalyst downstream of the DOC; an ammoniaoxidation (AMOX) catalyst downstream of the SCR catalyst; a DOC poisonmodule configured to estimate an accumulation of a first poison on theDOC, and configured to request regeneration of the DOC when theaccumulation of the first poison on the DOC meets a first predeterminedpoison accumulation threshold corresponding with a minimum desirable NOto NO₂ oxidation efficiency of the DOC; an SCR poison module configuredto estimate an accumulation of the first poison on the SCR catalyst, andconfigured to request regeneration of the SCR catalyst when theaccumulation of the first poison on the SCR catalyst meets a secondpredetermined poison accumulation threshold corresponding with a minimumdesirable NOx conversion efficiency of the SCR catalyst; and an AMOXpoison module configured to estimate an accumulation of the first poisonon the AMOX catalyst, and configured to request regeneration of the AMOXcatalyst when the accumulation of the first poison on the AMOX catalystmeets a third predetermined poison accumulation threshold correspondingwith a minimum desirable ammonia oxidation efficiency of the AMOXcatalyst.
 18. The exhaust aftertreatment system of claim 17, wherein:the DOC poison module is further configured to estimate an amount ofpoison being released from the internal combustion engine and an amountof poison being released from the DOC, the estimate of the accumulationof the first poison on the DOC being based on the amount of poison beingreleased from the internal combustion engine; the SCR poison module isfurther configured to estimate an amount of poison being released fromthe SCR catalyst, the estimate of the accumulation of the first poisonon the SCR catalyst being based on the amount of poison being releasedfrom the DOC; and the estimate of the accumulation of the first poisonon the AMOX catalyst is based on the amount of poison being releasedfrom the SCR catalyst.
 19. A method for estimating conditions of andregenerating exhaust aftertreatment system components, comprising:estimating an accumulated quantity of a poison on a first aftertreatmentcomponent; commanding a regeneration of the exhaust aftertreatmentsystem if the accumulated quantity of the poison on the firstaftertreatment component meets a first threshold associated with aperformance characteristic of the first aftertreatment component;estimating an accumulated quantity of the poison on a secondaftertreatment component; and commanding a regeneration of the exhaustaftertreatment system if the accumulated quantity of the poison on thesecond aftertreatment component meets a second threshold associated witha performance characteristic of the second aftertreatment component. 20.The method of claim 19, further comprising: determining an amount of thepoison entering the first aftertreatment component, wherein estimatingthe accumulated quantity of the poison on the first aftertreatmentcomponent is based on the amount of the poison entering the firstaftertreatment component; and estimating an amount of poison beingreleased from the first aftertreatment component, wherein estimating theaccumulated quantity of the poison on the second aftertreatmentcomponent is based on the amount of poison being released from the firstaftertreatment component.